10. The M-113 Creature
This sad-looking creeper earned a spot on our list almost entirely by being in the right place at the right time. In "The Man Trap" – the very first Trek episode, beamed out to the universe on September 8th, 1966 – the Enterprise visits the desolate planet numbered M-113, only to lose several crew members under mysterious circumstances. The culprit turns out to be this shape-shifting beastie, the last of its kind, which has been killing people to feed its serious salt cravings. There were much scarier foes still to come for Captain Kirk and his crew, but we'll always remember the M-113 Creature as their very first.