brown sugar, salt, paprika, black pepper, garlic powder, onion powder,ground mustard, cayenne if you want, red pepper flakes if you want, cumin, cloves, coriander, etc......
The first 7 ingredients are, in my opinion, mandatory. The amounts are kinda important too. Also, I like to use olive oil or canola oil or any kind of mustard spread on the meat first.
Any other BBQ questions?