PSP, and PS Classics that can be played on VIta, and Vita games.
these below I like a lot, in no particular order:
Akiba's Trip
Muramasa Rebirth
Sword Art Online
DanganRonpa 1/2
Persona 4 Golden
Persona 3 Portable
Ys: Memories of Celceta
Crimson Gem Saga
The Legend of Heroes: Trails in the Sky
Wild Arms 1/2