This is sort of a game/slash challenge... Think of a basic science fiction plotline, describe it in two or three sentances, then list at least THREE films that fall into it's parameters... Okay, here are a few examples:
1). Radiation in one form or another creates a giant mutation of insect life. Scientists investigating them manage to stop their proliferation just in time!
The Giant Mantis
2) A group of isolated people are confronted with strange creatures that are multiplying quickly.
Island of Terror
Night of the Big Heat
Feind Without a Face
3) An astronaut crashes to Earth, and has become a monster on the loose.
First Man Into Space
Incredible Melting Man
The Quatermass Experiment.
How many can we think up?