I mix my own for pork, but for brisket, I use a local butcher shop's rub.
Bringhurst in Berlin, NJ, they sell it in 8 oz. take-out tubs, and they just call it "The Rub". They make a batch in a five gallon container every day, and generally sell out by noon or so, earlier on weekends. It's incredible on its own, but I often add a couple teaspoons of New Mexico, Guajillo, and Ancho powder.