I dunno, if I had to get three of my friends to help me take one guy out, he is probably someone I want on my side.

Chocobo - VII
Ramuh - VII
Shiva - X
Ifrit - VIII
Titan - VII
Leviathan - VIII
Odin - IV
Bahamut - VII

Whose your favorite non-classic summon? - Diablos

Whose your favorite one time summon? (i.e. only appeared in one title) - Duno if it counts, but I loved having 3 versions of Bahamut in FFVII

Who is your favorite Ultimate summon? (Crusader, KotR, Eden, Ark, Magus Sisters, Zodiark...) - Asside from the fact that I judge it to be way to weak, Ark takes it. Though I never use it for purposes other than to watch it as it takes way to long.

Which game did you enjoy the summons the most in? - FFVII, I didn't like the way they were implemented into the game play in most post-psx FFs, and the graphical effects in FFVII are just so much better than the SNES versions.