Whose your favorite non-classic summon?
Odin, although he wasn't in the first two games, I guess that's of no consequences since only Bahamut appeared in FFI and Leviathan in FFII. But yeah, he was always my favorite to find, from getting him at the Shinra mansion, the King in FFIV, the crazy ass underground passage of Galuf's castle in FFV, the weird ass temple in FFVIII.

Whose your favorite one time summon? (i.e. only appeared in one title)
GILGAMESH!!!!

Who is your favorite Ultimate summon? (Crusader, KotR, Eden, Ark, Magus Sisters, Zodiark...)
KotR, just for how insane it was at the time.

Which game did you enjoy the summons the most in?
Final Fantasy VII, the animations and battle direction was just so over the top.