The best IMO is.. Viper...

WELCOME TO MY WORLD

Really nice voice acting that is audible for both sides (even for ally it says DON'T GET IN MY WAY) and one can really see the effect with them green clouds. REALLY BADASS!

The worst, or the lamest IMO (not about their competitive effect but the voiceline only) is Killjoy

Why? Well, for the enemy it simply says YOU SHOULD RUN. Wow.. How kind. Really polite of Killjoy isn't it? And for the ally she simply says INITIATED . I expect something longer and memorable.

So what's yours?