For ribs and pork butt, I like Williams Rib Tickler Rub. MaxQue and SmokinMAINEiac have given me great personal concoctions, but they are not strictly commercial.
For brisket, I like Carl's Prime Rib and Roast Seasoning. For poultry, I go with Paul Kirk's Chikki Rub and like SmokinMAINEiac's derivative of same. For tri tip and other roasts, I use a Santa Maria Rub made from recipe.
I like others that I make myself from commercial recipes from the likes of Bob Lilly, Dr. BBQ, Paul Kirk, etc.