Jetpack Joyride is one of the more delightful jetpack-based games to come out this year -- and for a "limited time," you can grab it for free. The official Facebook page for the iOS App Store is offering the game at no cost for reasons unknown; probably as an altruistic gesture, since human lives are inherently enriched by the presence of propulsion-based backpacks.
There's no telling when the deal expires, so we'd suggest getting it ... like, right this instant. Seriously. Go.