I'm biased so I voted for support...
Anyway, I recently met an awesome person while in Team Builder. They were Jinx and I was Nami. After loading into the game, they type "NAMI" into the chat and I'm worried they might tell me not to suck or something, but instead they say "ARE YOU READY TO DO THIS?" Then they told me how they were planning to play against the enemy adc, which was nice to know so I could adjust my play style accordingly.
Needless to say, we dominated that game. They added me afterwards and while we haven't played together that often, I haven't lost a single game while supporting them.