I had a nightmare about them last night, actually. They are sort of like zombies, except they're still alive and they can fly spaceships and also they rape you. Basically, they're really fucking scary. Here is an explanation. WARNING: clip contains spoilers.
2. Gremlins from, duh, Gremlins
I realize this is not a particularly scary movie, but when it was released, I was two years old. My parents rented it at some point when I was very, very young and for some reason let me watch it and it gave me nightmares for years. Like, I was convinced they lived under my bed, but only when the lights were turned off.
3. gremlin thingie from Cat's Eye
Again, this movie isn't scary, but I saw it when I was really young and it warped me for life. I think that, basically, this family takes in a cat and the mom hates it because she thinks cats steal your breath (what?) and she thinks this cat is stealing her daughter's breath or something (again, huh?) BUT it turns out that what's really happening is that this gremlin thing comes in through the wall and steals the girl's breath. The cat fights it, though, proving that cats are not, in fact, always evil.
4. Zombies from, um, any zombie movie
You know this. I mean LOOK.
5. tiny gremlin things from The Gate
I don't remember much about this movie, except these kids dig a huge hole or something in their backyard and evil things from the Hellmouth come out and try and sacrifice them or something. I don't know where the parents are. The only other thing I remember is that, at one point, an eyeball grows in this kid's hand and he stabs it with a piece of glass. That whole movie fucked me up. I saw it when I was like 8 WHY I DON'T KNOW. Hey LOOK, here's a clip. Wow, that movie looks awful. I kind of want to see it again.
BONUS: This isn't from a movie, but I used to have nightmares about pandas. They lived under my bed and would reach up from under, and they had glowing red eyes and long, sharp claws. Yeah, I don't know why.
So, basically, it seems like I mostly have a problem with zombies, zombie-like creatures, and gremlins. Good to know.