While not named on Supernatural, the trident or pitchfork appears on a number of occasions as a symbol of Lucifer and of Hell. When drawn with 3 lines through it, it can prevent a demon from de-possessing its human meatsuit, as well as act as a warding sigil.
Having fled his palatial home, Crowley has taken up residence in a ruined house, that has tridents painted on the walls and windows. When Crowley and Dean capture Brady in order to ascertain Pestilence's location, Crowley carves a trident into Brady's chest, telling Dean it will prevent the demon leaving the body.
Crowley: This bit of carving will tie our friend here down. No zapping off, no smoking out - locked in the meatsuit.
When Sam and Dean find Lucifer in Detroit in an abandoned building, he doodles a trident into a frosty window.
A variation on the trident symbol appears on the front door of Eleanor Visyak's warded safe house.
The trident appears among the various warding sigils in Bobby's panic room.
The drink Dean orders Crowley has a Trident in it.