Well, the obvious things are a sidearm of some sort; the usual suspects being a Walther and Luger.

But more importantly, a MG42 gunner would have equipment that would prolong the time he could maintain a high rate of fire; he would carry up to two (2) spare barrels, carried in a bangalore-like container. He would also find himself with a pair of thick wool or asbestos gloves to aid with the swapping of barrels rapidly and safely. He would also carry a cleaning and repair kit in a (usually) FeldGrau or Olive colored burlap bag, double strapped, which would contain all the necessary equipment to prevent the barrel from gumming up, and routinely servicing it. Finally, as the MG42 was usually handled by a senior man, such as an OberGefreiter, it would not be unusual for him to have some form of field glasses, doubly so if he was the leader of the MG-Truppe or if the MG-Truppe leader was hors d'combat.

EDIT: I need to stress that this is nominal, and an absolutely unrealistic amount of equipment for a single man to carry - given that the MG Truppe was at least 3 men in ideal circumstances, we can expect things like the spare barrels to go to the third man, while the bulk of the ammunition and field glasses would go to the second man in the team. The second man in the team habitually carried a side-arm as well. Its safe to assume that at most, the actual gunner would carry the cleaning kit, a belt of ammo, or a few assault drums, and the MG itself.