Well, maybe Ed Wood's 1959 classic isn't exactly horror, but it's still a must-see. According to Wikipedia, it's about "a race of extraterrestrial beings who are seeking to stop humans from creating a doomsday weapon that would destroy the universe."
Really? I didn't glean that, but there is a spaceship on a string, that catches on fire. It switches between night and day in the same shot, and the only set they use is a cemetery.
Pure cinematic gold.