I'm tall, lean, and have a very defined physique (the product of channeling my OCD into a workout regimen). I dress in mostly slim-cut dark clothes, have a fairly long and gaunt face, and my smile falls somewhere between "jaded" and "sardonic." I'm not unattractive, but the combination of an overlarge nose with an otherwise lean face ruins the overall effect somewhat, and the permanently grim expression probably doesn't help. I've been told I look cold, taciturn, and focused...so yes, actually, my overall look matches my personality fairly well.
That said, I'm not exactly the emo boy that some people tend to instinctively label me as. I'm an eternal pessimist and a clinical depressive, but my attitude towards life is much more...reserved than your average emochild. So I guess in that sense, my personality isn't quite a match for how I'm outwardly perceived.