I never got to try New Coke; I was too young to be aware of much of the world.
I tried the Crystal Pepsi, though. Looked like 7-Up but tasted like Pepsi. It didn't feel right to me, as I suspect it didn't for everyone else.
One cola I've always wanted to try is Vanilla Coke, which they still sell, but only in crates of 24 cans. I don't want to buy and waste that much soda just for a sample.