First appearance: Godzilla vs. Gigan (1972)
Alien cyborg Gigan is a walking death machine. Instead of hands and feet, he's got giant steel scythes, and a deadly buzzsaw runs from his chest to his alien-cyborg private area. In other words: do not hug. Gigan can zip around at Mach 3 on Earth, but in space he really hits the gas, travelling at Mach 400 encased in a diamond shell. (That's 400 times the speed of sound, which sounds like a lot, but the speed of light is nearly Mach 900,000.) Gigan holds the distinction of being the first enemy to make Godzilla bleed.