In a small bowl whisk together chili powder, cumin, onion powder, garlic, powder, salt and pepper. Pour beef broth into slow cooker, place the roast, then sprinkle the roast with the seasoning mixture. Cover and cook 8-10 hours on low.
Remove the roast and trim off all fat. Shred with two forks and return it all to the juices in the slow cooker, and cover with lid, to cook an additional 30 minutes. Drain meat through a colander.
Serve in warm flour or corn tortillas. Garnish with chopped lettuce, monterey jack or cheddar cheese, sour cream, guacamole, tomatoes, salsa, cilantro, lime juice and hot sauce.