Attack of the Giant Leeches is a gem...so is The Killer Shrews!
Quite a bit more recent, but you cant go wrong with Killer Klowns From Outer Space. Another BEAUTIFUL one from roughly the same time period is Dark Heritage. Good luck finding a copy of it anywhere but the internet, but if you can track it down its more than worth it. Its not really very good per se, but it has a magic all its own.
Oh! Dungeon of Harrow! That one is my Halloween night staple, I watch it every year. Its old, cheesy, god awful - and without a doubt among my favorite movies.
Man, I could go on with this for hours....