Oooooo....I like the sounds of this one!!
Jigsaw
http://www.imdb.com/title/tt0330489/
Totem
http://www.imdb.com/title/tt0211050/
Near Death
http://www.imdb.com/title/tt0371846/
The Incredibly Strange Creatures Who Stopped Living and Became Mixed-Up Zombies!!?
http://www.imdb.com/title/tt0057181/
(A lot of people defend that one by putting it under the "so-bad-its-good" banner. Even though it probably has the greatest title of all time, the movie has NO redeeming qualities. I couldn't even laugh at it.)
Essence of Echoes
http://www.imdb.com/title/tt0295244/
The Covenant
http://www.imdb.com/title/tt0475944/
(Not sure if you can really count that as horror...but it definitely counts as God-fucking-awful)
I left off the "so bad they're good" ones and just went for the worst of the worst. If we're keeping the fun kind of garbage in here, you can't forget:
- House of the Dead
- Killer Klowns from Outer Space
- Puppet Master vs. Demonic Toys
- ANYTHING by Ed Wood (Plan 9 being the obvious)
- Dark Heritage: The Final Descendant (this one actually transcends "bad" and goes on to a whole other plain of being)
I can come up with more if you're so inclined :D