Well, actually a gun that SHOOTS pool noodles.
A "Pool Noodle" is a 3" round, 5' long hunk of polyethylene foam used for kid games in the swimming pool. I originally bought one to use as insulation on my A/C Freon line ($1.50 vs. $7.00 for the Home Depot kind). I mentioned this on another group and people started commenting on various other uses for Pool Noodles, insulation, shock-absorbing material, spacers for infant car seats, etc.
One application is shown on the video below. Take a PVC pipe and seal it at one end. Into a plastic bottle, drop some dry ice, water, and screw the cap on tightly. Drop the bottle quickly into the PVC pipe. This is the propellant. Just as quickly, drop in the projectile: Croquet ball, small animal, or, in this case, a Pool Noodle.
BOOM!
Video