A pulse cannon was a type of starship mounted or ground based directed energy cannon weapon.
The Tandaran Detention Complex 26 was defended by pulse cannons. They were the first targets hit by Enterprise NX-01 shuttlepod piloted by Trip Tucker during his liberation of the camp in late 2151. (ENT: "Detained")
Zobral's desert hideout was protected by pulse cannons. One of them was hit by two attacking Torothan cruisers, during a raid in 2152. (ENT: "Desert Crossing")
In 2370, Quark arranged for the Vulcan gun runner Sakonna to procure a dozen pulse cannons from the Pygorians for the Maquis, which were later mounted to two of the Federation ships they had in their possession. (DS9: "The Maquis, Part II")
The USS Protostar was equipped with pulse cannons. (PRO: "Lost and Found")