Adapted from here
serves 6-8

1 tablespoon chili powder 
2 teaspoons ground cumin 
2 teaspoons dried oregano 
2 teaspoons salt, or more, to taste 
1 teaspoon ground black pepper 
4 pound pork shoulder, excess fat trimmed
4 cloves garlic, peeled 2 onions, quartered
 2 oranges, juiced 
2 limes, juiced 
cilantro, garnish (optional)

In a small bowl, combine chili powder, cumin, oregano, salt and pepper. Season pork  with spice mixture, rubbing in thoroughly on all sides. Place garlic, onions, orange juice, lime juice and seasoned pork into a slow cooker. Cover and cook on low heat for 8 hours or high for 4-­5 hours.
Once the pork is cooked,preheat your broiler to high heat and prepare a baking sheet with aluminum foil. Use a fork to shred the meat into bite-sized pieces, and return the shredded meat into the slow cooker for a few minutes. Use a slotted spoon to transfer the meat to the prepared baking sheet, spreading it out evenly in a single layer. 

Reserve the remaining broth from the slow cooker.

Place the sheet under the broiler for about 3-4 minutes, or until the edges of the pork begin crisping up. You don't want to broil much longer than that because the meat will dry out. Remove the sheet, and use a spatula or tongs to toss the pork. Then ladle about 1/4 cup of the remaining slow cooker broth over the porkGarnish with cilantro. 

Serve immediately in tacos, burritos, salads, omelets, you get the idea.