Aw, shucks; I’m humbled. 
Here’s another one that hasn’t been mentioned yet: Barn of the Blood Llama. That’s right, folks. LLAMAS! Crazed llamas which spit toxic cud and hate menstruating women!
And you thought Monty Python was making it up!
By the way, http://www.badmovies.org is a damned fine website for this kind of stuff.
Well, then you probably wouldn’t like Ticks, a 1993 movie about giant ticks. Not exactly the scariest movie, but got me on the creepiness factor.
I’m having trouble thinking about a giant whatamicallit that hasn’t been used in a movie. How about giant evil clowns. Yeah, I know there’s a movie about evil clowns from space, but they weren’t giant. Maybe a circus clown could get extreme radiation from a set of juggling balls and that will make him grow to be enormous and go crazy. Then he rampages throughout the fairgrounds.
I can’t believe how many people have seen Food Of The Gods besides me.
I don’t remember the name of it, but there was a giant rat movie about a huge rat in some people’s house. Pregnant female, I think. Also a Stephen King short story made into a film about giant rats in a textile mill. “Graveyard Shift”? My absolute favorite of these would have to be “Them!” Classic, IMO.
When I was in college, we always wanted to make ATTACK OF THE GIANT TINKERTOY MONSTER. Shot of the tinkertoy monster from below, looking up; then a shot from the third story window of a building, looking down, at people running away in panic. Movie would be dubbed, of course, using only Asian students in the various roles.
We couldn’t get the dough, sadly enough.
Attack Of The Giant Killer . . . Glacier!
I like long movies.
It could be Nightmares (1983). This was actually a “Twilight Zone” sort of affair with four seperate stories. The last one was about a nice little family that had a rat problem, so they laid some traps and killed one. But then they find out that there was actually an 8-foot rat living in the basement or something (like you could miss that) and it is might upset that they killed one of its babies. For some reason, the little girl of the family can talk to the giant rat. Like so many other things, they never bother to explain how that works.