How obscure are we talking here? Cause there are bands that don't have mainstream success but I wouldn't call them UNKNOWN (Between the Buried and Me, Cynic, Devin Townsend), then there are truly obscure bands (I, Omega being the main one I can think of at the moment).
For the truly obscure, I, Omega is Protest the Hero-esque, and they are very good. Only one album out so far, from when their name was The Syncope Threshold. Looking for a singer right now though, so I have no clue when the next album will come out.