Definition wise, I'm just going with dudes that aren't on the radio/MTV/VH1 etc:
Stoupe, C-Lance, Alchemist, Anno Domini, Havoc, Skammadix, Vanderslice, Stu Bangas, Apollo Brown, Sean Strange, Necro, araabMUZIK, Jaisu, Mov3ment, Sid Roams, MTK, Aktone, Molemen, Snowgoons, 4th Disciple, Thomax (easily the most underrated underground producer EVER)