I use Bad Byrons for pork butt when I am lazy, and it tastes great, but no injections. Here is one I have been tinkering with. If you drop the brown sugar to 1/2 cup it will take most of the sweet out.

Mexican Pulled Pork Rub
For 10-15 pounds of pork butt. Mustard, corn oil, or olive oil can be rubbed on meat prior to rub.
1 Cup brown sugar
½ cup kosher salt
1/3 cup teaspoons chili powder
¼ cup cumin
3 tablespoons smoked paprika
3 tablespoons dried oregano
2 tablespoons granulated garlic
2 tablespoons freshly cracked black pepper
1 tablespoon cayenne pepper