Recently my dads vacuumcleaner started dropping into pieces (wheels were broken off, hose-thingy had a rip in it and the auto-winding mechanism for the electric cable stopped working).
So my dad decided to buy a new one and knowing me he asked if I would like to keep the old one to screw around with.
So I carefully RIPPED it open and removed every piece, after which I reassembled the engine, button, power-dial and the electric circuit.
I drilled holes into the engine's plastic housing and connected the electronic circuit by using those plastic ehhh(see ascii) ----- becomes -[-]--- attachment loopy things.
I don't have any pictures available right now so I'll use my 3d sketch as a reference;
The idea is that the engine blows air into a valve connected to a y-valve which stores the air in a metal cylindrical container.
After switching off the engine you would pull the lever which would change the air pathway from engine-container to container-barrel which would shoot a projectile of my choice.