Hmm ok well here's mine. Different form most. In order, my top 5 would be:
1. NIN
2. Recoil
3. VAST
4. Bad Religion
5. Stabbing Westward
Honorable mentions (alphabetic): 12 Rounds, A Perfect Circle, Aphex Twin, Chemical Brothers, Crystal Method, Dead Kennedys, Einsturzende Neubauten, Garbage, Godspeed You Black Emperor, Linkin Park, Marilyn Manson, Massive Attack, Metalica (pre-Load), Moby, Mum, Muse, Nirvana, Pink Floyd, Plaid, Portishead, Prodigy, Radiohead, Rage Against The Machine, Rammstein, Razed In Black, Rob Dougan, Sponge, and Tool.
My music collection is quite large. 139 bands, 9 composers, and 38 soundtracks. 20gb of music; 5000 files. That's after I cut back to save space too.