Shadow Complex has a multipurpose foam-gun, decent price
Chair Entertainment's Donald Mustard was at Comic-Con, and he talked a bit about Shadow Complex, the side-scrolling action title Chair's working on with Epic.
There's a video over on Destructiod featuring Mustard discussing weaponry, speed runs, and the foam gun which allows you to cover an enemy with quick-hardening foam or use to create a path of sorts to reach certain platforms.
Game's out later this year on XBLA and will run you 1200 MS Points ($14.99/£10.20).