Things I haven't used but thought about as concepts.
if you use ai you can fuck right off :)
Gimmicks (something to build a character around)
Soul collector - a character who carries and collects a lot of shoes. Of victims? For themselves? Who knows.
Potter painter - a character painting, onto plates and other pottery, scenes to trap them in time or shape the future.
Heads or tails - a character who can only make a choice through a coin flip. Is it by design or discipline?
Candle - someone who grows shorter in the heat. Maybe even taller in the cold.
Looks (both fantasy and reality)
Netting - hair that extends out into a giant fishing net.
Wings - hair that is acually someone's wings alike a biblical angel.
Key accessory - either the one item they always reach for, or one accessory type in all the colours. Works best for characters that change outfits often.
Quirks (things to graft onto a character to make them more dimensional)
Oops all pockets - they have absolutely everything and anything in their bag or pockets. Could be extremely useful stuff like band-aids, or it could be extremely random like the wooden case of a carpenters pencil.
Oops no pockets - the person who always needs someone else to hold their stuff.
Snack attack - forever seeking out or holding a snack.
Compulsive artist - if there is a surface and a medium, this character will have to make their mark.
Second screener - needs constant stimulus from multiple places.
Hubris reincarnate - constantly believes that they can do the best in any feild without struggle.
Puppeteer - someone who moves their hand like a puppet to talk sometimes. Maybe to diffuse tension or to say something that they're awkward about.