Black Flag..Live '84
Slayer..Reign in Blood
Metallica..Ride the Lightning
Flag b/c it's a live album with Henry Rollins and they hit all the real good stuff they did with him (and some before, such as Nervous Breakdown).
Slayer b/c I had it when it was the current album. Nearly 30 year fan of them, and one of the best metal albums of all time..even though it doesn't have my favorite song by them on it.
Metallica b/c it is the first metal tape I ever bought, when it was the current one. Also the first show I went to on the Damaged Justice Tour in 1989