Tremors (1990): Pretty much a worm just trying to get a taste of that (Kevin) Bacon. You can't forget the pole vaulting scene or when that little girl nearly gets eaten off her pogo stick. Classic.
I like to believe that the worms are radioactive biological experiments created by the U.S. government to fight the Russians by releasing them into Siberia. In this case, we thought it would be fun to have them set loose in L.A.