Bike Seat Dagger
The "dagger" consists of a 10-inch piece of solid steel, machined down to a spear-like point and then welded to the end of the bicycle seat post. It is easily concealed when the seat post is clamped in place in the bike's vertical seat-post tube.
Remember when dealing with cycling subjects, separate them from their vehicle to reduce the risk of them quickly accessing a hidden weapon.
Thanks to: Ofcr. Pete Beckwith for showing this weapon at the Street Survival Seminar