Elvira, Mistress of the Dark-
My daddy has always been in love with her so I saw this over and over. Once you get over the outfits it is a very funny movie IMHO (And all my cult movies seem to be Halloween ones so far)
The Last Unicorn-
Not a forgotten cult classic, but a cult one just the same I think. The magical story, animation, music and voices just make a fairy tale all their own :3. The book version is wonderful, but the movie just has a special magic. It was made in japan for the US voices and never shown at the movies there oddly enough...
Watership Down-
The book is a classic, but the cartoon movie is one that still to this day has a following that both loves and is still a bit afraid of it. Many fans were scarred for life from parts of the more bloody fights and spooky scenes and symbols foretelling bunny death in a more than Boober-ish way. I'm not sure if it did well in the past or not, but Watership Down has a place in history in my book