Because it samples Grace Jones' "Slave to the Rhythm", I would have to go with "Bonita Applebum" (UK Remix). OK, maybe there are better ATCQ efforts but the vibe, sample and length (9+ minutes) make it a gem.
p.s. While there are so many memorable Rakim tracks and lyrics, I always like to point out the overlooked "What's on Your Mind". It's fookin' poetic genius. The images so vivid.