Celes was one of the few characters that had SO many options, I couldn't decide how to build her. I split her ELs between Shiva and Phantom. I was toying with ways to work speed into her build effectively, but couldn't decide how to do it since it would come at the expense of other stats.
Because Celes for me won't be tanking endgame, I want to do a Siren-heavy build next game. I'd love to do her magic/speed/stamina, but Phantom is Celes's only stamina option.
I'd love to figure out how to do an effective Crusader build, too.
Celes can also equip Seraph.
There are so many things to do I just don't know what to do with her or where to start!
TERRA IS A BAD B!TCH. I gave her 2/3 Maduin, and 1/3 Bismark. Next playthrough, I would totally pump all her stats into Maduin because, endgame, she wasn't doing anything physically at all (when it came to bosses, anyway). Her magic output was so ridiculously high that even on split target spells, she was doing close to 8k damage. Morphing became unnecessary late game.
Gem Box makes her go and go and go. Crystal Orb... whew!

Her only problem is that she's slow. as. mud. Not quite as bad as Cyan. And she can't cast Rerise.
Kefka's tower was the most fun dungeon in the game, IMHO.
Another question: WHEN is Merton useful?
There's only one Minerva, and only one Apocallumina, so the hack really forces you to choose. Not that I'm complaining - I think it's brilliant - I just have to have nine million more replays, now. <3