How experimental do you want? Einstuerzende Neubauten made some interesting records in the eighties (and later as well). I enjoy Five on the open-ended Richter Scale.

All Bitches Die by Lingua Ignota is absolutely terrifying, in a good way (if you enjoy unhinged screaming and beautiful melody, and who doesn't?). It's not a crappy hip hop album, but deals with artist's experience of abuse and with revenge, hence the title.

Edit: Wait, you want brilliant experimental music? Check out Mr Bungle. The s/t is... funk hardcore metal, but good, I guess. The other albums, idk sinister lounge music perhaps?