In a medium bowl, stir together lime juice, agave, soy sauce, olive oil, cilantro, garlic powder, salt and pepper.
In a large ziplock bag, add chicken thighs. Pour the majority of the marinade in the bag, reserving 1/4 cup separately, and seal. Shake the bag until the chicken is coated.
Marinate in the refrigerator for 3 hours, up to overnight.
In a medium bowl, stir together ingredients for the mango avocado salsa. Set in refrigerator until ready to serve.
When ready to cook, heat up the grill. Grill skin side down, until crispy and brown, approximately 6 minutes. Turn and cook on the other side until cooked through, approximately 5 minutes. Baste occasionally as the thighs cook on both sides.
Serve immediately with salsa. You can even shred the chicken thigh meat and make tacos out of it!