Quick, cheap, effective.

Ronnie Lee Gardner, convicted twice for Utah murders, was last person executed by firing squad in US in 2010
As an effort to resume executions in South Carolina, a state once known to have the busiest death row in the nation, the South Carolina House of Representatives voted on Wednesday, May 5, to add death by firing squad to the state's execution methods

Gary Gilmore - Wikipedia
“In Utah, firing squads consisted of five volunteer law enforcement officers[13][14] from the county in which the conviction of the offender took place. The five executioners were equipped with .30-30-caliber rifles and off-the-shelf Winchester 150-grain (9.7 g) SilverTip ammunition. Gilmore was restrained and hooded, and the shots were fired at a distance of 20 feet (6.1 m), aiming at the chest.”