[Sosha]

Anima = female
I thought this poll / thread was a favorite Aeon of all FF's, since it said 'aeons, sumons, espers etc..'
Since it's just from FFX, I guess it's a bit easier.
My fav from 10 would prolly be Ixion.
I think it has a nice originality to it, plus he's a new form of the Thunder god.. what isn't to like? 7's version of the thunder-summon, Ramuh, was pretty weak.. An old man standing atop a suddenly formed rocky slope, emitting streaks of lighting from a staff.. meh

Ixion, of course because of the graphics and technology, had a nice look and manner about him. His horn being unicorn-ish and also doubling as a lighting rod was a nice touch too.. I dunno it was just a nice classic mix on a regular every day animal being elevated to god-like prestige

Bahamut also looked really nice in 10's version and the fact that u're able to control all these summons in this Final Fantasy was great, a really nice addtion to the short-scene summon action of previous FF's. Bahamut is known to be the Lord of the Dragons.. so he had to look glorious and powerful.

Yojimbo was a nice Aeon, cept for that u had to pay out the ass to get him.. but he also didn't really do much. You had to pay him to make every move, even though it could be as cheap as 1$. He also had an 'overdrive' type ability in X-2, Zanmato, I think it was called; Why wasn't he or didn't he do it in X? Maybe the SE-FF developers just added it to X-2 because they knew u're supposed to again, face off w/ the aeons.
The magus sisters were alright too, prolly the best in terms of controlling the aeons because you get 3 more characters, that get very powerful attacks after you level up enough. They have their own attacks, and their own personalities, which u can somewhat control. They did look goofy, being bug-like, but the idea of 1) controlling the aeons and 2) having 3 more aeons to control.. was a very nice idea. I'm glad they're starting to make the Aeons / Summons of new era - Final Fantasys more involving and interactive.

Anima was ok too, cept that I felt bad for her :O Bondage type Aeon O_O