1. In a glass measuring cup, squeeze limes, yielding 1/4 cup of juice.
2. Add the garlic, pepper, olive oil, and cilantro and stir.
3. Place the shrimp in a medium bowl and pour the cilantro lime marinade over the shrimp.
4. Let the shrimp marinate for 10 to 15 minutes in the refrigerator (do not let them marinate for more than 30 minutes as the acid of the juice will alter the texture of the shrimp).
5. When marinated, alternate cherry tomatoes, mushrooms, and shrimp on four skewers.
6. Grill the skewers over a medium heat for 3 to 4 minutes on each side until the shrimp are just cooked through.