The Beast from 20,000 Fathoms...
This film really sets the stage for the next 2 decades of monster movies. Having not seen it in a while, you forget about the carnage and mayhem the Rhedosaurus wreaks.
This is a significant film in cinema history, it's easy to point to Kong (2 decades earlier) but this movie brings us the nuclear themes, Ray Harryhausen and a ton of plot elements that now almost seem cliche since they have been copied so much.
The Lighthouse Attack is one highlight:
There is another scene that a lot of people kind of laugh at, but i really think that it is kind of perfect. You have a cop trying to stop the Beast with his revolver. I guess the criticism is "what does he hope to accomplish with that?", but this is a creature no one has seen before, and he is doing his best to protect the citizens.
I give this movie 4 out of 5 radioactive isotopes (but that's only because the other one is the only one of its kind outside of Oak Ridge)