Favorite Alien Guest - Who is your favorite alien guest?

[NeoMatrix]

[color=#000000ost_uid0]I have seen some good answers, but what I was going for are characters you only see once that pretty much represent the alien species. Like when Voyager visits a planet, one or some of those aliens have lines and a name. And after that episode, you never see them again. That is what I was trying to go for, but you all have been doing a good job.[/colorost_uid0]