There are relatively few well-known machinima voice actors. While most (if not all) machinima creators eventually spend time voice acting and often do that work for one another, the world of "primarily a voice actor" folks is relatively small. Among them, however, Jesse Cox is one of the best and most popular. He's very skilled and can convey immense amounts of characterization with his instrument: his voice. We get the chance to see him do his thing in Garrosh vs. Vol'Jin.
In this video, Jesse's conveying one of the hallmark conflicts in Cataclysm. Racial leaders Garrosh and Vol'jin have some harsh words for one another, which will eventually lead to significant ramifications for the Horde. Jesse's working on a series of guided tours through Cataclysm, but this episode stands out because of the opportunity to let him voice act both characters. As I think you'll see, he does an amazing job. As interesting as I found the lore to be, I found his performance equally entertaining.