Bike derby

Also known as "Foot Down" a bike derby is a contest, the goal of which is to be the last person still riding their bike. Modeled somewhere between a Demolition derby and a Roller derby, a bike derby adds the element of maintaining balance on a bicycle while causing other contentants' to lose their balance and step or fall to the ground. When a contestant touches the ground, they are considered out of the derby.
Bike derbies often involve, roughly in order of popularity:
# drinking alcoholic beverages
# an arena defined by the spectators' bodies
# audience participation
# personal injury
# property damage, primarily to contestants' bikes
# cheap bikes
# costumes
Additionally, a newer trend of 'Ghost Biking' has become part of a derby. A 'Ghost Bike' is a riderless bike that is often rolled into the mix by someone on the sidelines. The intention of this is to knock someone off their bike.
History
While historically based on a popular children's pastime, the modern bicycle derby was first implemented in Minneapolis, MN by the Minneapoilis Mafia. Since that time, bicycle derbies have spread through the industry and to events such as the Single Speed World Championship.