I think most of the posters in this thread need to use a dictionary because I don't really see anything underrated in this thread
As for my two cents, there was this death/thrash band called Incubus that released a record in like 1987 that's totally fucking insane. The drumming in particular is something else. I think they don't get much love because I guess they technically were a Christian band. Also Sacrifice from Japan. The first record is retarded heavy. The slow parts sound very Celtic Frost, while the majority sounds like a faster Motörhead
For those of you who are into avant-garde black metal à la Deathspell Omega, Portal and Blut Aus Nord, you should definitely try Dodecahedron and their eponymous album that came out at the beginning of 2012.