For shrimp, chicken or skirt steak tacos...

1 whole ancho chile, stemmed and seeded
1 dried chipotle chile, stemmed and seeded
1 teaspoon whole cumin seeds, toasted
1 teaspoon dried Mexican oregano (found at Latin markets)
2 tablespoons kosher salt
cup brown sugar
3 cloves garlic, peeled and coarsely chopped
Canola oil, to thin to a paste

1) Toast seeded chiles in a 400 F oven until fragrant and slightly darkened. Soak in cold water then pat dry and finely chop.
2) Toast cumin seeds and then macerate it with the oregano in a spice grinder.
3) Combine the finely chopped chiles with the rest of the ingredients to make a paste. The use of a mortar and pestle will help.
4) Thin a small amount of the paste with a tablespoon or two of canola oil and rub on your protein of choice before grilling.