In a large mixing bowl, combine shredded chicken, cheddar cheese, diced tomatoes, diced onions, chopped cilantro, jalapeno, cumin, chili powder, salt, and black pepper. Stir well to combine.

Warm corn tortillas in a dry skillet over medium-high heat for about 10 seconds on each side. This will make them more pliable and easier to roll.

Place about 2-3 tablespoons of the chicken mixture onto each tortilla, spreading it out in a line down the center. Roll the tortilla tightly around the filling and secure with a toothpick. Repeat with the remaining tortillas and filling.

Heat vegetable oil in a large skillet or deep fryer to 375°F (190°C). Carefully place the taquitos in the hot oil, seam side down. Fry for 2-3 minutes on each side, or until golden and crispy. Remove from the oil and drain on paper towels.

Serve the taquitos warm with salsa, guacamole, or sour cream for dipping.