In Undertale, I would either be Sans (because I'm really lazy sometimes) or  Frisk (for reasons even I'm not sure of, but those quotiv quizzes don't lie, do they?). Personally, though, I like to think of myself as purple Frisk because my soul color is purple (perseverance), and I am apparently like Frisk.

(I can also be Chara if you make me mad. Don't make me mad, please. Cleaning up the blood and hiding the body afterwards if soooo time-consuming. :P)