Just the yellow wave that it makes. Yes it kills all the other teams bots but I think it team coloured would make it easier for people to understand it. )Coloured of the person who used it.
It's not really necessary because when the ejector goes off one of three things happens: 1) You see whoever is about to push it and are able to jump if it is an enemy. 2) You don't see anything until the ejector goes off, at which point something arounds you get destroyed. 3) You don't see it until you're being blasted away. In all scenarios, you know what happened, unless you're very, very new.
Either or its not a bad suggestion. On the times im not playin azazn id like to know who hit the anni besides having to go look or wait for the micky cantor.
^this. blue beams for icemen, red beams for hotshots. maybe a colored sky animation as well. this way, we immediately know who pressed the annihalator when we are on teams of no-mics.