I'm surprised nobody mentioned it yet (I might have just missed it mind you), but The Room
is a brilliant puzzle game that takes great advantage of touch-based controls.
One of the very few tablet experiences I would actually describe as worthy of one's gaming time.
Other great suggestions I'd like to echo are XCOM (turn-based strategy being suited perfectly for tablets) and The Walking Dead S1. Also, Infinity Blade is quite entertaining.
Too bad some if not most of the great tablet games (the few of them that exist) are iOS exclusives.