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We have two iPhone 3G phones. At this point, I'm going to say that the must have app is Apple Store, so I can quickly order whatever new phone they release.
 
Lets be serious here. In several countries they are just now getting the iPhone 4. I remember reading back in 2010 when the iPhone 4 was hitting the shelves in America and the UK the smaller European countries were just getting the iPhone 3G. So not everyone has the same opprotunities.

Anyways.. Some good applications would be Facebook, Pandora, Angry Birds, Vevo and Opera Mobile.
 
LOL i have the iPhone 3G, so i can relate.

Focus on getting low-CPU apps, like Facebook. Trust me, an iPhone 3GS is a much better buy.
 
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