Why is Angry Birds so famous? I have much better apps than that and Angry Birds is STILL on the top paid. Maybe it's just the feeble minds of people, wanting the famous app?
Anyways, I'd recommend Cartoon-Wars, as said above. Mega Jump, Undercroft (If you enjoy rpgs) Pocket Tanks, Fastar. Those are the ones I had the most fun with.
Also, get the Free Apps Finder. It finds newly "free'd" apps in the App Store.