If you want melodic death metal, Dark Tranquility is awesome. Any album of theirs would be a good choice (though "Projector" is fairly different from their usual style).
Amon Amarth is really good. Their most recent album "Fate of Norns" is great.
Arch Enemy is a good one; great guitar work.
Children of Bodom is a great band: fast, melodic, technical, intense. If you like the style of Children of Bodom, try Kalmah and Norther as well.
Moonsorrow from from Finalnd is great; melodic death with sort of unique feel to it.
Early Septic Flesh would probably work, if you don't mind a slower tempo. (Later Septic Flesh is also good, but it's not death metal any more.)
If you enjoy the more progressive/technical side of things, try Misanthrope or Arsis.
Armageddon's album "Crossing the Rubicon" is awesome. (Later Armageddon is more power metallish; I don't know if that's your thing or not.)
"Heartwork" era Carcass is also great.