There are so many great ones. I'll limit my recommendation to two just so that my post will be punchy for its directness and simplicity.
Dunhill Flake and Rattray's Old Gowrie. Dunhill Flake for its delicious citrus directness and Rattray's Old Gowrie for the immense complexity; a bowl of Old Gowrie in one of my pipes changes three times before it's done it's that complex.