When I lived in Maine we would grill almost every day in the summer, I loved it! Nothing like catching a nice striped bass then throwing it on the grill for dinner that night. We tried to grill a lot of stuff, and for fruits it doesn't get any better than pineapple on the grill.
Trim the outer skin off of the pineapple and cut into long sections avoiding the hard inner core. we would usually cook on the top part of the grill while the meat was cooking then transferring it to a hotter part to finish cooking. Makes for a great side with your meal, or for a dessert. You can also try a sprinkle of brown sugar, cinnamon, or both. Either way it is so delicious. The heat from the grill cuts down the acidity of the fruit and makes it super sweet. It's also a big thing in Brazil, I went to one restaurant where the pineapple was sprinkled in cinnamon placed on a spit, grilled whole and served for dessert. they bring it out on the skewer and cut you off a slab.
Also another fruit I found works well are peaches. Take a nice ripe peach and cut around to half it. Remove the core and grill on a slotted metal pan. When the peaches become soft they're ready, but first add a sprinkle of brown sugar to the pit. This is SO good! It's actually the only way I eat peaches.
I highly recommend trying both of these if you haven't already, I promise you... you will not be disappointed!