The first one I've seen is Blizzard. For some reason, Mages using Blizzard do not cause Bruisers to react at all, despite doing it right in front of them. The new exploit I've seen today was Alliance using the Timbermaw transformation and attacking right in the middle of Gadgetzan:

A minute or so after the screenshot, the transform effect wore off, and the Bruisers aggroed the offending Hunter.
I assume neither of these ways to kill players in Goblin towns existed on retail, and therefore assume abusing Blizzard/Timbermaw to kill people is a ban-worthy exploit.