Rubber is pretty out there, when it comes to weird as fuck movies. Old boy was also mentioned. A good movie, I think, but weird nonetheless.
When it comes to "funny weird" I think "Roboter der Sterne" (Robot of the stars) is one of the more bizarre ones I have seen. It's a film cobbled together out of a japanese TV show with no budget at all. The effects get repeated over and over again and look like a kid playing with toys in a bathtub, the acting is hilariously hokey and the story makes no sense. But the best part? The german dub. I wouldn't be surprised if the voice actors didn't even have a script. It's just bad puns, references to german cities, that couldn't have been in the original, and deliberate misreading of lines. It's a mess. Trash at its finest.
When it comes to disturbing weird, I have to go with Possession from 1981 starring Sam Neill and Isabelle Adjani. It never even got translated over here and I hear it was banned in the US for a long time as well.
This movie is just... exhausting. People constantly yelling, no story, just madness that somehow escalates into murder and tentacle porn ... of all things. This movie has no story and I am still torn if it has something to say at all. It just seems like pretentious, annoying madness to me. But it has an impact. You just want this bizarre mess to stop and finally start making sense.