Guenidier Tactical Fleet
The HMS Guenidier (GTF-002) was an Intrepid-class starship, formerly of the designation USS Foxhound, which was stolen from Starfleet Command orbiting Earth in the year 2395, by the crew of the former USS Guenidier. It was later renamed in honor of the crew's original starship, which was a Saber-class vessel. (Star Trek: Guenidier)
The crew subjected the ship to numerous modifications. The most prominent being the addition of two Dilithium Focused Phase Cannons. Using capacitors built into the above decks they are able to fire once and then have to spend several hours charging. The firepower rating is equal to that of several photon torpedoes.
A second modification was provided by the Klingon house of K'Vorash, in the form of a cloaking device. The main issue with the device is the interface, which drains power from the warp engines and results in a max warp capability while cloaked of Warp 4.