I've got to go with Blank. The cutscene in the Evil Forest really made an impression on me the first time I saw it. It's also really cool watching him integrate himself back in to the group later on down the road and trying to catch up on what's been going on.
There's also something I've been wondering about him. Doesn't he look like he has skin like Sally from The Nightmare before Christmas? Stitched up? Or is that just his outfit?
I also love Ruby's lines. I remember one time I actually answered Baku with "We're going to kidnap Queen Brahne" too many times so I could see the scene where Ruby comes in and says we're gonna be late! Or something like that
I made a poll so we could have a tally of everyone's favorites. I intentionally left Zidane out. Given his role in the story, I didn't want that poll option to overshadow all the others.
I found this really cool Amano artwork of Tantalus and wanted to share it: