The Devil Bat
This campy, entertaining cheapie from PRC Pictures features Bela Lugosi as a chemist who plots an elaborate revenge scheme on his business partners, whom he feels have cheated him out of his share. To this end he develops a mutant breed of vicious, oversized bats and trains several of this breed to home in on a special chemical which he then blends with shaving lotion. Presenting gifts of the lotion to his partners as a peace offering (and browbeating them into splashing it on themselves while in his presence), he subsequently unleashes his monstrous pets to tear them to pieces. Believe it or not, this was one of PRC's more successful horror programmers, spawning a the sequel Devil Bat's Daughter.