I've added three pictures to this post.  What none of these pictures show is just how tender and juicy this meat was.  OMG, this was excellent!!!  I served this two different ways (in tacos and on nachos) but I could think of other ways to serve it...along side some cilantro rice, rolled up in a burrito, in a quesadilla.  You get the point -- This is very versatile.

Slow Cooker Barbacoa Shredded Beef
slightly adapted from Group Recipes

3 pound tip or chuck roast, some fat trimmed off (leave some for flavor).
1/2 a yellow onion quartered
2 large garlic cloves, cut in quarters
2 jalapeno, chopped
2 Tablespoons chili powder
1/2 teaspoon garlic powder
1/4 teaspoon onion powder
1/2 teaspoon pepper
salt to taste
2 cups of water

Place all ingredients in slow cooker.  Set on low and let cook for 7-8 hours until very moist and it shreds easily.  There should be enough liquid to keep it moist.