Don't have fun at the expense of others.
I don't care whether you consider something like Kha support or Nami jungle fun. Do it with the consent of your team. If you are playing with friends, that's fine, but be sure to tell other players. No one likes losing because some guy thought it would be fun to ignore what the others want to do. Even if it's normals, some people don't find the stuff you do fun. If everyone but you is unhappy, then either you are very optimistic or ignoring your team. I don't care whether you feel like Maokai ADC is the best thing to do. I do care when you do it out of nowhere and I just want to play to win.