My favorite brisket rub is currently roughly equal parts Bad Byron's Butt Rub, Superfinely ground coffee, and brown sugar. However, if that sounds like too much of a PITA, I'd say go with very simple salt, pepper, garlic powder, and onion powder and really learn the meat/process of a brisket before playing around with "exotic" rubs. If you want to take that 'simple' and bump it up to full rub status, add in some paprika and some sort of sugar :P
Left tap: Myrd's IPA
Right tap: Heffeweizen
Kegged: Blimey's ESB, Apfelwein, Ed's Haus Pale Ale
Fermenting: Air, but soon to be Ode-to-Arthur and more Apfelwein.