Other stuff nobody's really mentioning:
-TxK: Download only new version of Tempest 2000!
-Killzone Mercenary: The good Killzone game. Has good single player and multiplayer modes.
-Freedom Wars: Monster Hunter style action-RPG, but with a faster pace and more action game-like game play. In addition to killing big mecha-monster things, there's also battles against rival human clans. Has online co-op and deathmatch.
-Musou: Take your pick with Warriors Orochi 3 Ultimate or Samurai Warriors 4. Although Dynasty Warriors 8XL has been patched to run/sound better, it's a weaker port compared to the other two.
-Sonic Transformed: The best racing game on the Vita, although I prefer more arcadey and kart style games to Wipeout.
-Hot Shots Golf: Self-explanatory.
-Rayman Origins: Great port of this 2D platformer.
-Virtua Tennis 4: May be hard to find now. Looks amazing and plays great.
-WARNING UGUU ALERT-
-Akiba's Trip: Crazy otaku game where you run around Akihabara and get into brawls, where the goal is strip enemies to their undies, which kills them if they're vampires. Yeah. Plays like Way Of The Samurai and is from the same developer.
-Hyperdimension Neptunia Re;Birth: Turn-based RPG that takes the various video game consoles and turns them into anime girls. You play as Neptune, based on the unreleased Sega console, and fight/ally yourself against versions of the Playstation, Wii, and Xbox. The story is nonsensical and humorous and the dungeons can be pretty hard if you go after the optional ones and/or try to take on the optional harder enemies.
-Senran Kagura Shinovi Versus: Musou-style beat-em-up with the perv factor dialed up to 11 off the charts. How much? Too much for Van Cruncheon to handle!