If you answered ‘get hassled by TSA agents’, you’d be right, but you could also do what [Mski] did and make a pocket dart gun! [Mski] used a 10mL syringe and a clear BiC pen body.
As stock, the Pistol Splat featured an incredibly strong spring and an unrestricted barrel, giving it plenty of performance capability. With some finagling, it’s capable of shooting a Nerf dart ...