Tajtiq

From Memory Alpha, the free Star Trek reference.

A tajtiq was a type of long knife used by Klingon warriors.

Worf used his tajtiq to fight Jem'Hadar on Vandros IV. (DS9: "To the Death")

In his duel with Gowron in 2373, Worf fought with a tajtiq. (DS9: "Apocalypse Rising")

The weapons were never named on-screen. In both cases, the script of the episodes feature Worf fighting with his mek'leth. It is unknown, why mek'leths weren't used as suggested in the scripts.