Bad guys I guess. The last time I played one was an AU Yozak who was very sadistic and only appeared in RP chat about 6? years ago. He was a looooot of fun. I'm kind of surprised I've never played one for real. Oh, I guess I did play an AU Ulrike with split personalities and one of them was kind of like a more intense Drucilla. Sort of. I find them kind of hard to work with because they introduce so many permission issues and I like being in the moment.
I don't always muse well with stoic characters. I'm not sure if I lack the voice as much as I just want them to talk more. I guess I like talkers. I don't mind writing them in fic.
But I like having a variety so, as soon as it seems like I don't play a type I'm usually trying to play that type? I don't know if it always successful mind you.