Appears in: The Beast from 20,000 Fathoms (1953)
Scariest moment: Rampaging the streets of Manhattan, the huge dinosaur withstands military gunfire as it crushes its way through buildings.
Weakness: Radioactive isotopes.
Before anyone accuses The Beast from 20,000 Fathoms of cribbing all of its ideas from Japan's Godzilla, consider this: Beast was released a year earlier than Godzilla. So is it actually the other way around? It appears so, but, frankly, who gives a damn?
Both films are monster movie blasts in their own right, though only one (Beast) has creature effects from Mr. Ray Harryhausen. And only one (Beast, again) features the wicked plot development of the monster's blood, let out by a soldier's bazooka fire striking the Rhedosaurus' scaly throat, turning human bystanders into beastly humanoids, albeit briefly.