The App store is jam packed with iPhone apps - we've previously covered our Top 10 best free iPhone apps, our pick of the 10 best free iPhone games on the planet and many more.

Our complete guide to the best iPhone apps links to all the best apps you can get your hands on.

But what if you just want to know the 10 apps that every iPhone user absolutely must own?

Then read on...

01. Tweetie £1.79 Our favourite Twitter client

We know that you might not be interested in a client for the microblogging service Twitter, but Tweetie is such an excellent example of how apps make the iPhone great that it takes our top spot nonetheless; Twitter was born for the iPhone.

Tweetie

Tweetie lacks only push notifications (though you could add that with an app such as Boxcar) to make it the ultimate Twitter app; it can geotag your tweets, let you view conversations, supports Lists, the new retweet feature and more.

Buy from the iTunes Store

02. Documents To Go £8.99 Word, Excel and PowerPoint editing

Documents to Go has the best word processor we've seen on iPhone, letting you create and edit Word docs while retaining formatting. It can work with Excel and PowerPoint documents, too, and the Premium edition lets you grab attachments from Gmail or Exchange servers.

Buy from the iTunes Store

03. The Guardian £2.39 Get your news on the go!

We're often asked why you'd spend money on an app that lets you do something that's free through Safari. This app is a good answer. Not only can you tailor the news that is delivered, but it's simple to use and you can cache stories to read offline when you're on the Tube.

Buy from the iTunes Store

04. TomTom UK & Ireland £59.99 Turn-by-turn directions

TomTom

There are cheaper apps that add turn-by-turn navigation to the iPhone 3GS (the £26.99 CoPilot Live app will happily get you from A to B) but it should come as no surprise that the app from TomTom is by far the most polished. It lacks live traffic info, but we hope that's coming soon.

Buy from the iTunes Store

05. Facebook £FREE Social networking client

The great thing about this app is that it lets you keep in touch with friends and upload photos from the iPhone's camera straight to Facebook. It also offers push notifications too. Now as soon as a friend comments on your status, you'll know.

06. Reeder £1.79 The best RSS reader

This little app syncs with Google Reader, a service for reading RSS feeds from your favourite sites. Though the interface looks a little sparse, it's actually stuffed with features, and since there are lots of Google Reader clients for the Mac too, you can keep your feeds in sync.

Buy from the iTunes Store

07. Mobile Allowance £0.59 A super billing assistant

Whether your iPhone came from O2 or Orange, this is a fantastic app for keeping track of how much of your monthly allocation of minutes and texts you have used, plus any extra charges. We installed the free O2 one, but went back to Mobile Allowance as it's much cleaner.

Buy from the iTunes Store

08. Instapaper Pro £2.99 Offline reading

You know how you often come across articles on the web that you want to read, just not now? Ping them to the free Instapaper service, then use this app that caches for offline reading for you to read later. There's a free version too, though it lacks the tilt-to-scroll feature.

Buy from the iTunes Store

09. RedLaser £1.19 The ultimate price checker

This app uses the iPhone's camera to take pictures of barcodes, then looks for the product online to check prices. Amazon results are first, but it also supports Google Product Search to query a huge number of other online stores. Just don't let the staff in HMV catch you!

Buy from the iTunes Store

10. National Rail Enquiries £4.99 Rail journey planner

Sure, you can use Safari to muddle through the National Rail's website to find times, but, while it's expensive, this app is an essential investment for regular train-users. It helps plan journeys, optionally remembering your favourite stations and even favourite journeys, and shows the live progress of your train.

National rail

Our favourite feature: tap a button marked 'Next train home' and the iPhone will work out where you are, where your closest station is, and when the next train leaving for your home station departs.

Buy from the iTunes Store

-------------------------------------------------------------------------------------------------------

Liked this? Then check out 20 best iPad games we want to see ported from the iPhone

Sign up for TechRadar's free Weird Week in Tech newsletter
Get the oddest tech stories of the week, plus the most popular news and reviews delivered straight to your inbox. Sign up at http://www.techradar.com/register

Follow TechRadar on Twitter