Nowhere does there exist such a disparity in function as there does between the different kids of smartphone apps. They can be used to save your buns from driving too drunk, and now they can be used to shoot people. Of course. Laser tag for our post-laser age, the Xappr or Micro-Zappr Gun can attach to your smartphone and turn any place into a battlefield, at any time.
Less uncomfortable legal implications than going to children's laser tag and less pain than paintball, these guns connect with your smartphone and create an augmented reality shooting game.
You can play a single player mode with aliens, zombies and the usual bad guys that anyone who wants a gun to attach to their iPhone will probably be familiar with (read: me).
There is, of course, also player-to-player combat, which will include more absurdly fun tools of destruction like grenade launchers and pulse weapons, etc.
Feel free to pre-order one from the Xapper website for a cool $45. They will be released in Spring and are compatible with iPhone, Android and Windows Phone operating systems.