Superman III - RoboVera
Holy hell...this scared the ever lovin' crap out of me when I was a kid. There i was, cheering on The Man of Steel....he just finished fighting his own evil self (which was kinda creepy in it's own right....and probably the closest we'll ever get to a cinematic Bizarro!) and he was back in bright colors fighting for truth, justice and the American Way. He tracked Ross Webster and gang to their Supercomputer hideout and things start to go sour. The computer (designed by super-genius Gus Gorman!) basically goes all Skynet and takes on a life of it's own. Unfortunately for Ross's sister, Vera, she's snagged by the computer's tracker beam and turned into a horrifying cyborg with some computer super powers. I was horrified. That damned robotic nightmare plagued my dreams for weeks.
The Princess Bride - R.O.U.S
Rob Reiner's seminal fairy tale has it all: Adventure, Revenge, Love......and the dreaded ROUS's. What's an ROUS? Rodent Of Unusual Size, if you must know.....denizens of the dreaded Fire Swamp! After Wesley (whom we just found out was alive!) and Buttercup roll down a giant hillside, they escape Prince Humperdink's forces by running into said Fire Swamp. Immediately after she asks him if they should be worried about the ROUS's, Wesley replies he does think they exist. Que a big ol' nasty ROUS jumping and attacking Wesley. These rats freakin' huge and nasty and if you get scared by a li'l ol' rat in a sewer, you are completely screwed if you come across one of these!
Oliver! - Bill Sikes
If you've seen the wonderful 1968 film, then you know exactly what I'm talking about. The inimitable Oliver Reed plays the incredibly creepy Bill Sikes. This man makes your skin crawl from the get-go, but as the film wears on, you realize that this guy isn't just a hard ass criminal....he's a bad man....he's a very bad man (to quote Billy Mumy). Towards the end of the film, Bill goes full on Jack the Ripper and we're fully well aware that we are in the presence of a man who will do horrible things to anyone who gets in his way.