Going to try this thread again:
Travis: ISFP: I initially though INTP due to his Otaku/nerd stereotype, but his motivations and action are not Ti/Ne, they're Fi/Se. Fi I was somewhat uncertain of until I recently got finished the second game, where it was clear that he was Fi driven (both in his lust for revenge and emotional anger at the lsot of Bishop, and the whole "assiassins are people not tools!" speeches he gives). Se is obvious since whenever he isn't killing other assassins he's caught up in the act of constant physical pleasure: watching poorn, watchin perverted anime, practising wrestling, living here and now, etc.
Sylvia: ESTJ or ENTJ: E is definite, considering that she is a manipulative con artists capable of changing her personality when it suits here, and her cold and controlling demeanor makes Te dome most likely. Not sue if she's more Si or Ni though.
Shinobu: ISTJ: I and S stright off the bat, she's too quite and unassuming to be an E, and by the second game she wants to serve as Travis's apprentice. ISTJ in general seems to fit here well, although I wouldn't entirely rule out F ot P.
I'll type the other assassins later, unless someone else wants to do so before I do.