in each category that you can NOT live without:

Thrash: Slayer - "Hell Awaits"

Death: Obituary - "World Demise"

Black: Profanum - "Eminence of Satanic Inperial Art"

Traditional Metal: Iron Maiden - "Powerslave"

Hardcore: Cro Mags - Age of Quarrel

yes I'm bored...

First

thrash: vio-lence eternal nightmare
death: cannibal corpse - tomb of the mutilated
hardcore: minor threat - minor threat
traditional metal: iron maiden - number of the beast.

bored.

thrash: testament - practice what you preach
death: grave - soulless
hardcore: hatebreed - satisfaction is the death of desire
traditional: judas priest - painkiller

Thrash: Tankard - Chemical Invasion (while there are many thrash bands i enjoy more than them, this is the best thrash album ever released IMO)

Death: Deicide - Legion

Black: Marduk - Panzer Division (i actually think 98 percent of black metal is lame, but this album rules)

Traditional Metal: Iron Maiden - Piece of Mind

Hardcore: Misfits - Earth A.D. (fuck the subgenres, this album owns all other hardcore recordings)

Grind: Napalm Death - Scum