Got 3 seconds and a normal bic pen and a rubber band? Then you might want to check this out.
Step 1: Materials
All you need is a normal BIC pen (with the cap) and one rubber band.
Step 2: Place the rubber band on your fingers.
Take the rubber band and place it one your thumb and middle finger and spread them apart so that the rubber band it taut.
Step 3: Insert the pen
Slip the cap inbetween the rubber band. Make sure that clip is fully on the rubber band.
Step 4: Fire!
Pull back the pen and the cap will go flying!