"Grease 2" starring Michelle Pfeiffer before she got all super-famous. Despite this elaborate bowling number, I never saw this film.
"Staying Alive," the sequel to "Saturday Night Fever," was directed by Sylvester Stallone. Even though it's all about making it on Broadway while wearing a headband, I never saw this film.
"Jaws 3-D" had the shark ultimately crash through the giant aquarium glass of one of those Southern Californian marine-parks. In 3-D! I saw this on a date in the theater when it came out. It was gravely disappointing. Both the film and the date.
"Troll 2" has gazillions of views on YouTube. But I haven't seen it.
Warwick Davis. Ice T. "Leprechaun in the Hood." Haven't seen it.
"Scream Blacula Scream," the sequel to "Blacula." I probably saw this as a child because pre-cable television used to show movies like this all the time. *sigh* The 70s--you really had to be there.