I'm not really an expert but fruit does is where the bulk of my carbs come from. So IMO,
1) Any low fiber fruit is good. Bananas are probably #1 due to the relatively high caloric density. Cantalopes, honey dew melons, peaches, and nectarines are also good. To add some quick calories, dried fruits such as rasins, dates, and apricots work well.
2) I like grapefruits. They are very low on the glycemic index and have lots of fiber and pectin which help you stay full longer. Also, they have lots of vitamin C to help repair those sore muscles and keep you healthy. Some say they even have nutrients that help oxidize fat. I also like pineapples. They also have a fair amount of vitamin C and fiber and have anti-inflamatory properties.
Tomatoes and avocados are also fruits. They have very low sugar levels. Papayas are very good in that respect too. They also help digest protein.
3) I think its best to eat a wide variety of fruits, but if I had to pick one as the best overall, I would probably choose the apple.