I dunno if there's a thread about here somewhere; apparently not, and even if there is, I'll have to dig it up, hmm well do I see a search here, no, I don't, even if there is, evidently I shall have to search for it too; but never mind that!
I mostly listen to metal. Though I'm also fond of classic rock and classical. I love:
Iron Maiden, My Dying Bride, Arch Enemy, Anathema, Empyrium, The Gathering, Megadeth, Dark Tranquillity, Carcass, At the Gates, Cadaveria, Windir, Mayhem, Tristania, Behemoth, Paradise Lost, Pantera, Marduk, Black Sabbath, Children of Bodom, Nightwish (older stuff), Metallica (older stuff).
Among the non-metal stuff, I love Led Zeppelin, The Beatles, Guns N' Roses, Pink Floyd, The Rolling Stones, The Who, Lynyrd Skynyrd and Queen.
What're your favourites?