I don't know if this really counts as a physical feature, but I find that the eyes make all the difference in the world. Regardless of what your physical physique may be, if your eyes don't seem engaged and alert then I'm not buying it. Too often my friend's will ask me if I find some guy on a magazine cover attractive (I assume to learn about how the gay folk operate) and more often than not the guy's eyes and smile will make him look like a giant, unappealing doofus despite being six-packed out.