I especially like Anomaly, which is a tower offense game -- in an interesting reversal, you direct a convoy that has to traverse a route (that you can set out) while being attacked by 'towers'. I showed klik the intro, and when the main menu came up, she said: "Oh, it's a game? I thought it was a movie!"
Osmos is cool too, with a simple concept (get bigger by absorbing smaller lifeforms) set to Newtonian physics. The soundtrack is quite relaxing too.
Edge is lots of fun with cubes. Again, a very simple concept (roll a cube across a 3D stage to an end point), but harder than it looks. And again, the soundtrack alone is worth the price of admission.
(And while I'm on the subject of the tablet: I hate it when I click on a deep link in an email or tweet, and the target site immediately redirects me to the mobile version of the homepage because I'm on an Android device. The screen is big enough to comfortably display any site, and I didn't want the homepage -- I wanted a specific page! At least send me to the mobile version of the page I requested!)