There's always a guerrilla undercurrent with graffiti, but the Facade Printer, which tattoos images onto buildings with paintballs, really makes that explicit. And judging by its work, I'd say it has pretty good aim.
The German contraption, which is comprised of an pressurised barrel mounted on a two-axis turntable, can blast pictures onto walls from a distance of six metres. It's controlled by an on-board industrial PC running a custom touch interface.
Images can be loaded onto the machine with a USB stick, and they're printed by paintballs of many colours travelling over 160km/h.
The Facade Printer is an especially cool embodiment of the push to make art, not war. Of course, it's hard not to imagine how much havoc it could wreak in your local paintball league. More pictures and video at DesignBoom.