Films:
Alien
Aliens
Alien 3
Resurrection
Creatures:
Alien
Dog Alien (had that gross, too many ribs look - like the vomit demon from Poltergeist 2)
Resurrection Alien Warrior (different enough to be it's own design)
Alien Warrior (for me it's a less elegant version of the origina - but I like the rib textured skull )