At the moment I am in a period of no mains, mostly only play Team Builder (As I find Ranked to be so unbalanced at the moment, sometimes people just get decimated in their lane by an opponent that was several ranks higher last season but got placed low, so waiting for that to blow over).
But damn, Vel'Koz is so much fun as support, the poke is great, the slow is great, and the knock up is awesome if they jump your adc. Also the damage is rather good, even with Support items/talents.
Also Xin top is great fun, crazy sustain and damage.
All in all, having great fun just testing all the champions I got, that I bought ages ago and played like once and forgot about. And the game is a lot more fun when I change champion every match!