I noticed Mango Jell-O the other day - label said that it was a new flavor. Since I used mango nectar in place of the cold water when making it, I can't comment on how it tastes plain. A couple of years ago they came out with Pina Colada and Margarita flavors but I never found them in the stores. They do have Pineapple Jell-O, though, and I sometimes use coconut milk instead of cold water.
Oddly enough, the chain supermarkets in my area tend not to carry many flavors - I find pineapple, apricot, and peach only in a small independent grocery store. Not a big deal, since I often use plain gelatin and concoct my own jello with various canned and fresh fruits and juices.