Tegra Pinball is...pinball. It's noteworthy mostly because it's the only game we found that uses the Thrive's portrait mode to good effect. The others, we'll discuss below.
Sprinkle's design uses fluid dynamics to manipulate the environment and fight fires
Angry Birds and Sprinkle (the latter tasks you with putting out fires) are both brain teaser games where the goal of the interface is to provide an invisible translation layer between you and the game. Pick a trajectory / adjust the sprayer, and watch the results. Complexity is added through creative physics and fiendish puzzles.
Fruit Ninja is another highly popular title that utilizes an interface so minimal, it scarcely deserves the name. In Fruit Ninja, your finger is a blade. You slash fruit. Slashing more fruit simultaneously = more points, while slashing a bomb = instant death.
Blood and Glory: Sword and sandals meet Infinity Blade
Blood and Glory is a free Infinity Blade-style gladiatorial combat game with gorgeous graphics and a mostly touch-based combat system, but the game has trouble differentiating between offensive and defensive combat moves. It was the one title that felt a bit jerky on our Toshiba Thrive. (Reviews of the game itself vary)
Dungeon Defenders: Second Wave features all campaigns and game modes of the PC Steam release
Dungeon Defenders: Second Wave is an amazingly good free action/RPG 3D tower defense title. The interface, menus, and in-game commands are all well designed and player control, while somewhat awkward, doesn't require a high degree of finesse. DD's graphics and level design are both excellent; any fan of tower defense games who want a little RPG action on the side should grab this one.
DD's interface stands out as one of the better examples we encountered. It's not perfect -- the game badly needs a 'Confirm' button when launching the next wave of attacks, and falling into lava pits due to clumsy character controls is downright annoying. Despite these flaws, DD is a great game and a good example of how complex functions can be mapped to touchscreens, even if the formula isn't perfect yet.
Tenets of Touch:
Angry Birds, Fruit Ninja, and Sprinkle directly map movement to in-game results. Whatever direction you move your finger, that's the direction of your sword cut / bird trajectory. Sprinkle modifies this slightly--putting your finger on top of the crane moves it up or down, while resting a digit anywhere else adjusts the hose trajectory.
Blood and Glory still maps touch directly to action, but there's a bit more symbolism involved. Gestures are translated into certain specific movements and must be timed appropriately to be successful.
Finally, there's games like Dungeon Defenders. Unlike the other titles we've discussed thus far, DD essentially emulates a conventional control scheme on a touch pad, and does so rather well. This approach makes sense -- any time a new medium is invented, the first works created for it tend to be "ports" of existing projects -- an awful lot of early movies were films of preexisting stage plays, for example.
There are, however, significant limitations to a touchpad's ability to emulate a controller.