Painstik

From Memory Alpha, the free Star Trek reference.

The painstik is a Klingon ceremonial device, used to inflict pain. It is used in the Age of Ascension ceremony, where, in the final part, a young Klingon must walk between two lines of Klingons, suffering the painstiks, and reaching the other end, before he can call himself a warrior.

In 2365, Wesley Crusher, Data and Geordi La Forge re-created the tenth anniversary ceremony of the Klingon Age of Ascension for Worf in a holodeck on board the USS Enterprise-D. (TNG: "The Icarus Factor")

Painstiks are also used in the Sonchi ceremony to confirm the death of a Klingon chancellor. The chancellor's body is prodded with painstiks by the Arbiter of Succession and the contenders to become the new chancellor while issuing verbal challenges. (TNG: "Reunion")

The Ritual of Twenty Painstiks is a portion of the ceremony of the Day of Honor. (VOY: "Day of Honor")

Klingon guards used painstiks on Captain Jonathan Archer when he refused to be silent during his trial on Narendra III in 2152. (ENT: "Judgment")