The Ator films.
Robot Vs The Aztec Mummy (In fairness, this was originally part of a Mexican movie serial which was then edited into several "Aztec Mummy" movies for American release. This particular film consists mostly of "flashbacks" to the previous movies and has perhaps the worst moster vs monster fights in history).
Dracula VS Frankenstein (the Al Adamson film)
Assignment Terror (This is also known as Dracula VS Frankenstein, too. A Spanish film which is a fun throwback to the Universal monster mashes. Aliens revive the great monsters, a vampire, mummy, werewolf, and the Franken, er, "Feranksollen" Monster to help them take over Earth).
Battlefield: Earth
Manos, Hands Of Fate (although you may need to MST3K version just to get through it).
Anything by Larry Buchanan, especially his no budget remakes of Roger Corman's low budget horror movies. Yes, you read that right, someone thought it was a good idea to remake low budget flicks with even lower budgets.
Any killer body part movie (hands, heads, brains in jars, etc).