A heavy-duty weapon installed into the ventral end of death gliders. In principle, the Goa'uld cannon is a staff weapon, however it's size allows for a larger surplus storage of liquid naquadah, as it is capable of launching far greater bursts of plasma to suit the needs of the gliders.
These cannons can, in fact, be removed from a downed craft to permit the continued defense of ground forces after the glider has founded. Few creatures, with the exception of Jaffa, are capable of toting the enormous piece of equipment the required distance into battle, let alone fire it.
The Fifth Man - Teal'c detaches a Goa'uld cannon from the base of a crashed death glider to clear the way for the rescue of a Reole who has been captured by an insurmountable armada of Jaffa.
48 Hours - Fleeing Tanith's ground troops, Teal'c uses his cannon weapon against an Al'kesh piloted by the minor Goa'uld, and obtains his revenge.