Well, the first time I play through, I like to leave the names as they are, but the second or third time around? Nah, it's too much to resist by then. Compromise is good <3.

Anyway...

Zidane: Jitan

Garnet: Ada (From Ada or Ardor by Nabocov; Garnet looks like Ada.)

Steiner: Nalpk (An anagram of "Plank" I first gave to Tidus in FFX.)

Vivi- Mouche (A term used by a famous French transvestite to describe the silk flowers on his dresses.)

Quina: Spoot (Meaning "drat" or "sub-par"; from The Angry Beavers.)

Freya: Absinth (Which should have an e at the end. I just like the word.)

Eiko- Tot (German for "dead" also one of the characters in Weiss Kreuz.)

Amarant- Useless

Of course, for round three, I might have to try some new things. I like a LOT of the suggestions here. Especially Breine's.