I love the list.
I'm guessing you're well aware of both Return to Oz and The Dark Crystal being pure nightmare fuel.
Suburban Commando: when Gen. Suitor gets sucker punched in the balls, he turns into something of cross between the Creature from the Black Lagoon and Predator. Totally unexpected and scared me as a kid.
Darby O'Gill and the Little People: made in 1959 and the Banshee is still impressive and scary.
Robocop: the guy who goes swimming in the toxic waste and starts to melt. And then he pops like a water balloon when hit buy a car.
Terminator 2: when the T-1000 mimics the guard, stabs him in the head, and then stares for a few seconds as the guy bleeds and spasms like crazy.