Wow, if I didn't know what Fallout 3 was I'd think that it was a FPS from that trailer, yet again. Was the Pitt the only part of Fallout 3 which had a trailer which actually had the player talk to someone, or am I imagining that as well?
So apparently the Incenerator shoots fireballs... I have to say that I'm disappointed, though certainly not surprised. If they wanted a ranged weapon which lit people on fire they could have simply made explosive rounds that are filled with napalm (or something of the sort) instead of standard explosives.