Was a big fan of Chuck Schuldinger , even after he died. Though he did have a habit of recruiting bad guitar players (I didnt think much of Rick Rozz). Death Metal is hard to come by these days thats any good. I still on occasion break out my Napalm Death and Sodom (Baptism of Fire is just a kick ass song to me) albums.

In the way of Thrash metal bands, Id have to consider Testament tops on that list. Hard to beat Alex Skolnik's guitar playing or Clemente's drum style.

Another favorite, Coroner (more of a Technical power thrash metal band, but still good).

Slayer...classic slayer was good. Before kicking and rehiring Dave Lombardo became a usual thing. Id count Haunting the Chapel, South of Heaven, Raining Blood and probably Show No Mercy as their best albums. I felt Seasons was an utter failure for them (despite the fact it bred their first rather dull set of Music videos).

Other bands to consider

Exodus, Candlemass/Nemesis, MercyfulFate/KingDiamond(if you like the high screaming types), Carnivore (and its post-decessor Type O Negative), Draconian, Crowbar (if you can find any). Hellhammer, Cletic Frost, Iced Earth, and the like.