I'll edit this entry later with pics.
This is one of the easier questions for me, even though there are quite a few cool alternate costumes. Anyways, the honors go to....*pulls out envelope and opens it*
- Zidane's "Assassin Marcus' Cloak" alt. I know it's a ref to the endgame in IX, but for some reason my thoughts keep going to Assassin's Creed rather than FFIX.
- Mateus' "Light/Heavenly Emperor" form. It was an alt everyone was looking forward to and naturally, SE did not disappoint. Being a Mateus fan, I HAD TO GET THIS ONE DURR HURR.
- Firion's Devil!Headdress alt. *has no idea what it's actually called* I like that it's so colorful, first off; very Amano-ish when it comes to colors and also DEM HORNS are about as tall as WoL's. POSSIBLE COMPETITION, MAYBE?
- Design-wise, I think Lightning's second alt could have gotten more work, maybe made to look closer in appearance to the uniforms worn by PSICOM Huntress and SANCTUM Inquisitrix. It's one of those costumes that grows on you the longer you look at it. That said, I think the part that appealed to me the most were the stockings. I'm weird like that.
- Prishe's second alt was another I liked. I didn't play XI so I don't know what was the costume's original purpose. On Prishe though, it looks like something you'd wear to the beach.
- Ultimecia's Edea alt. From the moment I saw it, I pretty much fell in love with Edea's sorceress' outfit especially DAT HAT so naturally when news came out that this was her second alt guess who was a very happy fan. Still takes getting used to lack of wings though...
I'll probably add more later on when I think of any others.