Its a means of transportation.
Or launching your self into your enemies with great force
How do you download this?
I keep extracting but they don't show up in my game ):
Click the pictures of the guns to view the induvidual files or click the link at the bottom of the first post to view the entire pack on the RTB download system, and follow the instructions there. It is probably better to get the entire pack because of how the guns require the Alien Blaster to work.