I strongly feel that the 1992 sci-fi movie Mindwarp would be an excellent candidate for the HDTGM treatment.
It actually had the potential to be an interesting, though provoking, entertaining movie, and the presence of Bruce Campbell (post Evil Deads) and Angus Scrimm means it wasn't a totally "off-the-map" release.
But wow, it just ends up being pretty insane.
Blood drinking, near-incest, a strange mute kid covered in cold-sores, demon leeches, Matrix-esque plot elements, slight nudity, underground mutants who mine garbage (for some reason?), ridiculously dated looking (even for 1992) technology, highly amateur philosophy, and one of the most god-awfully terrible, drawn out "twist" endings of all time (seriously terrible ending).
There's so much to make fun of (including a lot of the acting performances.) Yet, probably enough interesting pieces of plot to actually spur some conversation. And it is sort of fun to watch, overall.
It's streaming on Amazon (for rent): http://www.amazon.com/Mindwarp-Bruce-Campbell/dp/B004AGKTL0
Even if it never makes it to HDTGM, fans of the podcast are probably the types who would enjoy (making fun of) this movie. Check it out!