[Matt the Merciless]

I tend to stick to a few core bands and don't branch out often, but here are ones I like:

GWAR
Devin Townsend (and all associated bands)
Metallica
Megadeth
Rammstein
Eisbrecher
Bloodbath
3 Inches of Blood
System of a Down
Scars on Broadway
Dream Theater
Symphony X
Mastodon
Amon Amarth
Alice Cooper (Though he's not very heavy)
Cradle of Filth
Dimmu Borgir
Nine Inch Nails (not sure if you'd count them)
Sonata Arctica