I picked up a jet pack first, then a rifle.
pressed J and I could use the jetpack, fly around and land.
Took off again and when I got a few 100 feet in the air, I now press 1 for the rifle, and nothing stopped me from picking it. I did loose the jetpack and fell to my death.
But that leads me to believe that somehow with scripting both could be used together.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit