What's an iPhone without apps? If you are seriously looking for some cool and must have application to fill up your iPhone, here is a list that you find quite useful in your day to day life.
Check out this list of 30 Best iPhone Application that you always love to install on your phone and don't want to be without.
Games
1. Angry Birds
Dangerously addictive but deceptively simple, Angry Birds lets you employ cartoon birds as weaponized projectiles in an escalating war against a posse of egg-stealing green pigs. (Don't ask.) Revenge relies on vectors and basic principles of physics, but the gist is to use a slingshot to angle an 'angry bird' at the smug little pigs. The real challenge? Putting your phone down once you've started.
2. Cut the Rope
Angry Birds dominated the App Store in 2010, but Cut the Rope — an equally addictive puzzle-like game — gave it a run for its money at the end of the year. Featuring Om Nom — a wee green creature with none of the rage of the Angry Birds but all of the aww! factor — Cut the Rope requires players to maneuver a piece of hard candy through a maze of obstacles and rope-cutting, and into the open mouth of an eager Om Nom.
3. Doodle Jump
One of the top-grossing apps of all time, Doodle Jump remains as compelling as ever. Tilt your phone to guide the adorably-long-snouted Doodler as he climbs a piece of graph paper, all the while dodging black holes, shooting monsters, and picking up goodies. Between the game's range of colorful winter, jungle, space and graveyard themes and its lack of a finish line, Doodle Jump is tough to quit.
4. Fruit Ninja
Who knew that a Ninja's worst enemy could be fruit? Apparently, Halfbrick Studio, the developer of this popular game. Just swipe your finger to cleave flying fruit in two, ideally before they hit the ground. Oh, and keep a watch out for bombs; mistakenly slice one, and it's game over. The app is integrated with OpenFeint (so you can compete with your friends), and it's an ideal app for commuters or for those stuck in a slow-moving grocery store line.
5. Scrabble
Hasbro's iPhone app version of Scrabble might be even better than Grandpa's board version. You can match wits against the computer, against online opponents, or against your friends via Facebook. Scrabble pros can have up to 50 games going at once, while newbies will appreciate the game's learning tools, including a teacher mode and a cheater option, which allows the computer to choose the highest-score word for you.
6. Plants v. Zombies
The thought of a zombie attack is enough to keep any sensible person up at night. But you know what's even scarier? Watching waves of zombies trampling your nicely manicured lawn. That national (or at least gardener's) nightmare is realized in Plants vs. Zombies, a perennial best-seller. Game rules? The zombies advance, you bombard them with any number of flora, including ears of corn and frozen watermelons. That's just common sense, right?
Lifestyle
7. Paypal
The Paypal iPhone app boasts several cool features, but two of them deserve some extra attention:
1. "Bump Phones" lets you send or receive money between your phone and another Paypal user's phone simply by bumping them together;
2. You can deposit checks directly to your Paypal account simply by taking photos of them. A bit more technology like this, and you may never have to step foot inside a bank ever again.
8. Amazon
The perfect shopping companion, Amazon's iPhone app lets users connect to their Amazon account with the tap of a finger. Fill your shopping cart or track the status of recently placed orders, or search the full selection of products available from Amazon.com. The app also lets you scan any barcode to search for comparison prices, or snap photos of a product (like those to-die-for shoes worn by the woman next to you) and quickly find it on the web.
9. Shop Savvy
A must-have for professional bargain hunters, the Shop Savvy app lets you compare prices and deals on the fly. Just scan the barcode of any item and in an instant you have a list that compares best prices online versus the local store — plus access to customer reviews, tips about coupon codes, and more. You can even share shopping lists via email, Facebook or Twitter, in case you want to encourage someone to buy that perfect something for you.
10. Epicurious
Making a stop at the grocery store on your way home? Pull up Epicurious, type in the ingredients you know you have at home, and then let the app do the rest. A virtual cookbook, Epicurious helps you plan small meals or family dinners on the go. One of the best features is the ability to see what percentage of people who made a recipe would do so again, so you can be sure that your chosen menu is worth the effort.
11. Mint
A virtual money-manager, Mint tracks your income, spending and investments after you enter your financial data to the password-protected site. It will also alert you, if you choose, should your spending go over a preset budget or if your credit needs attention. The site was featured as one of the best in 2010, and its app takes its robust planning services and delivers a pocket-sized financial advisor. Thankfully the service is free, as is the app, so the download won't push your budget further over the edge.
Music and Photography
12. SoundHound
Can't name that song? There are myriad apps to help, but we think SoundHound is the best. Boot SoundHound up and let it listen to the track for a few seconds and it'll spit back the track name. The app's good at picking up the beat even over ambient noise like a bar crowd or a casual conversation. Best part? It's totally free.
13. Pandora
Pandora was a great service on your computer, but it's even better on your phone. Having the free app means that you can discover new music on your morning commute, at the gym, or wherever you happen to be. If you already have an account, you can sign in and easily access any of the channels you created on the web. And don't worry if you created an awesome channel on your phone — it will all transfer back to your account so you can access it on your computer.
14. Bloom
Put your creativity to the test with Bloom, an iPhone app that lets users build their own visual patterns and unique melodies by tapping on the screen. The app is part instrument and part artwork, letting anyone be a full-fledged composer. Not feeling creative? Bloom can do the composing for you. There are also 12 different mood settings, random mood shuffle and a sleep timer, should your perfectly created melody happen to be a lullaby.
15. Mog
Though the U.S. still can't partake in the magic that is Spotify, Mog is a quite-capable imitator. With a free app and a $9.99/month subscription, Mog gives you access to a massive music library that exists in the cloud. Connect via WiFi or 3G to stream on the fly, or download tracks in advance to save for those days when you're off the grid. iPhone 4 users also get the benefit of background streaming, which keeps the tunes going while you fiddle around in other apps.
16. Photoshop Express
There's an awfully fine line between having too many complicated photo editing features on a device that fits in the palm of your hand and not having enough tools to get any real work done. Photoshop Express straddles that line quite nicely, thank you, by offering basic editing features, color adjustment, filters, a handful of essential effects and several borders. Best of all, it's free.
17. Camera+
If the iPhone's standard camera is like a digital point-and-shoot, the Camera+ app is like a high-quality SLR lens. Developed by a professional photographer, Camera+ includes a burst mode for action shots, an image stabilizer and even a timer for self-portraits. But the real fun begins after you trip the shutter. The app lets you manipulate your photos with crops, borders, color tints and retro effects. For the iPhone user serious about taking beautiful photos, it's $1.99 well spent.
18. ColorSplash
Go from amateur to professional photographer in the snap with ColorSplash. This iPhone app will convert any photo to black and white even while allowing you to keep specifically chosen details in color. Pinch-to-zoom lets you work with pixel accuracy, and when you're done with your tinkering you can share the results on Facebook, Flickr or Twitter. Your friends won't believe the photos didn't cost you a pretty penny.
Social
19. Google
Search is even more convenient with Google's iPhone app, which puts the web (and all of your favorite Google products, like Gmail, Maps, Docs, and News) at your fingertips. The app also employs voice recognition, letting users simply announce what they're searching for. Bonus item: one of Google's most interesting features, Google Googles, has finally made it to the iPhone, allowing you to use pictures to search the web for landmarks, products and more.
20. Skype
Skype uses your phone's data connection to make free calls to other Skype users. And unlike Apple's FaceTime video chatting feature that only works on Wi-Fi networks, Skype users can video chat with each other over a 3G connection. Add in low-cost international calling plans, built-in instant messaging functions, and CD-quality voice transmission and you've got this whole communication thing covered from just about every angle.
21. Facebook
Really, do we need to explain Facebook to you? Just know that the company's iPhone app brings all the things you love (or love to hate) about Facebook to your pocket, including that constantly updating list of your friends' links, loves, lunches, locations and more. Chances are, your friends have already joined the 150 million Facebook users as of October 2010 who used a smart phone to update their status, so get with the program.
22. Twitter
The big reveal about Twitter for the iPhone is that tweeting pictures has never been simple. Just point, shoot and share your snapshot with your entire flock of followers. As you might expect, all the other Twitter-ific things are present in the app, including the ability to DM people, @reply, post tweets, and follow breaking news.
Entertainment
23. IMDb
The app takes the already-popular website and puts it in usable, fast-moving mobile form. Every film tidbit you'd ever want to know is on IMDb, including cast lists, plot summaries and critical reviews. It's a one-stop shop for film buffs and trivia hounds, who can also search for showtimes nearby and even shop for DVDs through Amazon. You can even watch trailers for upcoming or just-released films, should you tire of reading.
24. Netflix
The Netflix app for iPhone comes on the heels of its iPad app, which was a monster hit. Subscribing to any of the monthly Netflix packages, which start at $7.99, gives iPhone users access to Netflix's instant streaming queue anywhere, even on a 3G connection (though a wi-fi connection provides a better experience). It's an ideal app for commuters or parents who want to keep their kids entertained on the go. One gripe: Customers can't update their DVD-by-mail queue within the app, a surprising omission. Let's hope that feature is part of the next update.
25. Kindle
It used to be that to access Amazon's 800,000+ Kindle library, you needed a Kindle. But the free Kindle app let's you buy and read any ebook available on Amazon, including a wealth of free classic titles such as Dracula, Treasure Island, and Gulliver's Travels. With many of the same features, like varying text sizes, word look-ups and free sample chapters, who needs an extra piece of hardware?
General
26. Google Earth
A pocket-sized version of Google's awesome web app, the Google Earth iPhone app lets you travel the globe while, um, traveling the globe. Handy for lending some perspective or just locating yourself in a new city, the app makes use of the same types of global satellite and aerial views you would get on the web. Just picture it: a third of the world's land mass, available for your viewing pleasure at the tap of a finger.
27. Weather Channel
Admit it — Apple's standard weather app just doesn't do it for you. If you want more than just the current temperature and the daily highs and lows, The Weather Channel's free app is a great alternative. Not only does it have all the basics, it includes tabs for hourly, 36-hour and 10-day forecasts. You can also read the latest severe weather warnings or check the radar for any dark clouds that might be headed your way.
28. Wikipedia
Think of it as the world at your fingertips. All of the content of Wikipedia, the user-created encyclopedia, nicely organized and made accessible in an app. Perhaps the coolest feature of the app, however, is the location option, which lets you instantly learn about anything (or everything) that happens to surround you at the moment. Curious about that odd building across the street? Or that bizarre statue in the park? Just fire up the app.
29. Yelp
Stuck in a new city without a clue as to where to eat? No worries. Just fire up your handy Yelp app, which locates all the nearby eateries, then browse by proximity, neighborhood, price, or what's open now. You also get easy access to Yelp's burgeoning collection of customer reviews, so you can avoid any clunkers. Not hungry? The app lets you find a whole host of other on-the-road necessities, such as bars, banks, drugstores, and gas stations.
30. Zipcar
A car sharing service like Zipcar is a cost-saving, green-living, no-brainer for anyone residing in a city. While the Zipcar iPhone app lets you find and reserve available cars in your vicinity, the truly awesome feature is the ability to unlock your chosen car's doors and honk its horn right from your phone using the virtual key fob. Necessary? Well, probably not. Cool? Absolutely.
You are most welcome to suggest any additions to this list. You can use the comments box below to make any suggestions.