Here's my favorite on grilled grouper or snapper, if you like a sweet/spicy combination. Very good for keeping light flavored fish from drying out on the grill, without the strong taste of some marinades. I wouldn't use it on something like amberjack that tends to have a stronger taste.
1 cup of Apricot preserves
1-2 tsp of crushed (not powdered) red pepper
2 tsp of Soy sauce
2 tsp vegetable oil.
Add all ingredient to a small pot and heat on the stove until the preserves melt into a thick sauce. Stir well to make sure the red pepper is evenly distributed throughout the thicker appricot preserve.
Brush periodically on each side of the fish while grilling. Add more to suit just before serving.
Very good on grilled shrimp too.