System of a Down - Selftitled -> for starting SOAD in general and never before heared vocals, lyrics, drums and arrangement

Slipknot - Iowa -> for having the most pressing, heavy & energetic tracks from slipknot and all other rock/metal albums
Pink Floyd - the dark side of the moon -> for countless hours on different drugs

Kidney Thieves - both albums -> for deus ex 2 soundrack and some of the most dramatic rock/industrial mixes i ever heared
Portishead -> both studio albums + live album -> well its portishead, what else i have to say? a class of its own
Massive Attack - Mezanine -> for a new style of triphop, just massive
im sure there are dozens more albums worthy the title "favorite ground breaking album", but that's all i can think of rightnow