Mix the oil, chili powder and 1 teaspoon salt together in a small bowl to make a paste. Pound the chicken breasts between 2 pieces of plastic wrap to about 1/2-inch thick. Rub the chicken all over with the chili paste.
Lightly oil the grill grates. Grill the chicken until firm to the touch and cooked through, flipping once, 3 to 4 minutes per side. Set aside to rest for 5 minutes, then shred the meat into bite-size pieces or cut into strips. Warm the tortillas on the grill and wrap in a kitchen towel to stay warm.
Serve the chicken tacos with shredded cheese, pickled jalapenos, shredded lettuce and/or salsa for topping.
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