Ben (1972)

This sequel to the rampaging-rodent chiller Willard (1971) stars Lee H. Montgomery as young Danny Garrison, a neglected kid who finds a new little friend in Ben -- an intelligent rat whose furry minions managed to slaughter most of the cast of the previous film. Proving that one can't teach an old rat new tricks -- just variations on the old ones -- Ben displays his affection for Danny by directing his posse to off anyone who torments him... in the sweetest possible way, of course, since this is a PG-rated endeavor.