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I don't know if these count:
Grabbers (2012) - Never seen anybody else on the forum mention it, I didn't look very hard but still. One of the best creature features in recent memory, and a total hoot.
Nekromantik (1987) - I think this is pretty infamous right? But not that many people have seen it, does it count? It's also actually pretty good.
Equinox (1970) - It got the Criterion treatment, does that disqualify it from your criteria? It inspired the much inferior film The Evil Dead.
Martin (1976) - When Romero gets brought up it's about the Dead trilogy, and rightfully so, but that leads to Martin being criminally underlooked. It's probably the most interesting take on the vampire genre.
Under the Roofs of Paris (1930) - Another one in the Criterion Collection. It's worth watching just for the transition of silent to talkie, and it's awesome.
Underworld Beauty (1958) - Most criminally underseen Seijun Suzuki film...also the only Seijun Suzuki film I've seen. I need to remedy this.