Bam called his old mayor "cleats" and I really hope he'll give me that nickname. I know I can make someone give me it, but I want to "earn" it. I don't know, that is just a really cool one. "Hiya, cleats! Whatcha want?" Awesome.
My Mabure characters all have nicknames. Avril is either Princess or just Avril to most of the town, although Rocco calls her brainiac. Nagako is june bug to most of the town, although Graham calls her amiga and Eloise just calls her Nagako. Rosaline is just Rosaline to most of the town, although Graham calls her mon amie and Wendy (who I'm trying to make her best friend) calls her Rose.
Danielle is just Danielle to everyone in Camazotz at the moment, and given her character I don't really intend on changing that (although T-Bone wanted to call her "Youngin" and "Bucko" at two different points).