I should contribute my own (especially because, no offense, there are a lot of new jacks in this thread):
Big Daddy Kane -- Long Live the Kane
Just listen to to Set It Off and Ain't No Half Steppin. Fifteen years later, those lyrics still haven't been touched. Louis Ave represent. Be sleepin on your rhymes til I start to snore.
Black Moon -- Enta tha Stage
Well basically I smoked a lot of blunts to this album. Also Who Got Da Props had everyone open. One of the best debuts of all time, and Buck's freestyles on Red Alert's show busted EVERYBODY up. Plus he represents FAP so act like you want it.
Tribe Called Quest -- Low End Theory
Not much to say except that it's simply one of the best of all time.
Common Sense (when he was Common Sense) -- Resurrection
Rhymes uglier than Craig Mack. His flow still needed work, and No ID's pops bought his beats, but still.
Off the top of my head...