We already have a thread on this. The search button could help making unnecessary threads again. But anyways, I'll answer your question. Paper Toss Waterslide Extreme Dropship Topple Space Deadbeef (though I thought it was crap) Tap Tap Revenge 2 Trace And Quest of Knights Onrush which is arguably the best free game on the store at the moment. I don't count lite versions, they usually frustrate me because I can't play any of the good parts.
Well, if you like puzzle games at all, the lite version of unblock me has a ridiculous number of puzzles. Its not "lite" at all, really, its a complete puzzle game -- the full version just has an unnecessarily larger number of puzzles.
Jelly Car is still one of my favorites, free or not! Atoms is still my favorite "avoid things" game (and it's got AGON integration!) Quick Turn is fun (though I like the Easter version better! Kraut is pleasant and has cute kids sounds! Dropship went free as did Topple
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=286516944&mt=8 is my favorite Sudoku game so far, no adds, only limitation is one game at each difficulty level per day. Lincoln!, Kennedy! and Obama are free versions of Masyu that I like better than the original (they're a tad easier because of the quotes...)