Preheat the grill to medium-high. Peel and remove the silk from the corn, then add it to the hot grill and grill for 2 - 3 minutes per side until it's charred and slightly soft.
While the corn is cooking, dice the tomatoes (I cut them into eighths), onions and avocado, and add them to a large bowl.
Allow the corn to cool slightly then cut it off the cob and add it to the bowl.
Finely chop the cilantro, then add that to the bowl along with the citrus juice, chili powder, salt and pepper. Toss to combine. Taste and adjust the salt + pepper as needed.
Serve immediately with your favorite chips (or on top of tacos, inside burritos, etc...the possibilities are endless!)