Difficult choice, really. That all depends on what your idea of sexy is. For example, I think Miyavi is cute and pretty, but his features are far too feminine for my taste. Hyde from 2002 on...well, that's just the perfect mixture of cute and sex appeal to me. Kaoru, too, but I like Hyde's height.
My mate prefers the more feminine boys though, so that's one more for Shinya (or rather Totchi, but he's not listed).