Given Sony and Valve's chummy relationship, I'm a bit surprised we haven't seen some version of Portal on the PS Vita. Fans have already gotten remakes of the game to work on PSP, Nintendo DS, and 3DS, so what's holding Valve back from making it official on a platform that could easily run the game?
Honestly, other than possible business reasons or lack of interest, I can't think of any. Plus imagine Portal 2 co-op, where one of you is playing on Vita while the other is on PS3. That would be pretty damn sweet, if I say so myself.