Quake Combat+ is a refinement & continuation of Quake, SMC & Quake 1.5, built on Darkplaces, aiming to provide the ultimate Quake singleplayer combat experience and perfect the existing works without straying far from the original design/balance to retain compatibility with the many great custom-made user maps out there.
One of four new powerups - Rapid auto shotgun upgrade. This is a very rare backpack drop and only lasts for the current level. It makes the starter shotgun a rapid beast, perhaps even better than the double barrel. Enjoy it while it lasts if you get lucky enough to find one.