Preheat grill to high. Wrap each ear in foil. Place on the grill and cook, turning frequently, for 10 minutes. Remove from the grill and let stand in the foil while preparing the butter. Combine butter, lime zest, lime juice, chipotle and adobo sauce (or ground chipotle) and salt in a small bowl. Carefully unwrap the corn. Serve with the butter.
Chipotle chiles in adobo sauce are smoked jalapenos packed in a flavorful sauce. Look for the small cans with the Mexican foods in large supermarkets. Once opened, they'll keep up to 2 weeks in the refrigerator or 6 months in the freezer.