Making the online rounds: A year-old BBC clip showcasing the potential deadliness of the air vortex cannon.
The vortex cannon is a super-blower of sorts, funneling the reactive energy of an exploded gas mixture into a directed, "smoke" ring producing a blaze of fast-moving air. It's quite fitting that the clip comes from the BBC's Bang Goes the Theory, which is like a slower-paced and brainier Mythbusters of sorts; this is a gun with quite a bang!
Of course, a gun that actually damages reinforced targets—not a pile of bricks presented as the last target—seems like a long way away. Aside from increasing strength of the acetylene-oxygen gas mix, something also needs to be done on the portability/form factor front. But for literally silencing that boastful man, Bang's Vortex Cannon should fit the bill nicely.