I have tons and tons of ideas I'd love to use in a roleplay but haven't gotten around to. Probably won't ever get around to using most of them because I always come up with new things I wanna play so the list just keeps growing, but that's fine. There are a few character ideas that come to mind immediately.
I want to play an intelligence vampire, a creature that drains people of their thoughts and memories and intellect for nourishment and leaves them brain dead.
I want to play a sentient suit of armor (yes, inspired by Alphonse from Fullmetal Alchemist) that can't actually move on its own and needs someone (another player's character) to wear it to be able to do things. Maybe with the sentience coming from some kind of ghostly possession thing, and the ghost can leave it and move around but not really do anything because it's a ghost.
I want to play a powerful wizard who has the personality of a cowardly and paranoid thief, all about secrecy and not trusting others and such. Probably gonna get to this one soon, since it could work in a lot of settings.
I want to play a character with some screwed up mutation thing where they have high regenerative abilities, such that they can regrow limbs over a day or so, and their body adapts in weird ways when it does major structure regeneration. Say an arm gets cut off by a sword, so it grows back with a chitinous skin to ward off blades. A leg gets blown off by a grenade, so a new one grows back that is very dense and blast resistant. It'd be amusing and often useless because the resistant limb would grow back after the present danger that destroyed its predecessor is gone.
I want to play a character that is a good guy and accidentally gets the soul or spirit or whatever of an average decent person stuck inside them or attached to them due to a fuck up that killed the unfortunate average chump, and of course the spirit would have to be able to talk to the person they're attached to, maybe also visible and/or audible to others depending on the world's rules for that kind of thing. I've seen plenty of things like this where it's a bad guy with evil spirits, or a clash between person and ghost alignment, but I've never seen anyone bother with average peasant getting bound in such a circumstance and I think it'd be neat to have it happen due to a good guy's mistake to add some moral weight and responsibility there.