cosmogramma by flying lotus, it's a bit abrasive/weird at first, but imo has a lot of groundbreaking music, shit is RIDICULOUS
dude, shit is really weird at first but it is good once you listen to it a little and get used to it!
maybe not underrated, but overlooked given illmatic, a lot of people never even knew nas existed other than illmatic
-ummagumma is pick floyd's best album -sailing the seas of cheese - Primus -Sleep's holy mountain - Sleep