This would be a hard choice for me: so many amazing characters to be!
A part of me wants to say Beatrix from FF9: despite the fact she was female. Warrior General that never loses a fight throughout the entire game and one-shots everything with 'shock break'? Nothing to complain about there!
There is also Kefka, but I lack his mindless purposelessness to actually emulate him properly.
Then there is 'ol Vivi from FF9 as well, what isn't to love about being a clumsy lil black mage?
Donnie did say about FFT, and then there is FFCC and FFTA to think about... Rem was a pretty amazing character in FFCC, however I can't go into detail about who or what he was since it'd be a pretty huge spoiler. Would fit me quite well in the 'crazy' department.
I honestly can't think of any FFT characters I liked, most were simply too transparent for my liking if I remember. Wonderful game despite such however.
Oh, also... Donnie. FFT: Stop Bracelet, Seal, Allure, Ultima, Shadow Stitch. The horrors shall never be forgotten.
