npc_tf2_ghost is an example NPC/Nextbot in the 2006 sandbox game Garry's Mod. It has the model of Mossman, a character from the 2004 VALVe game Half-Life 2. The NPC only walks around if a nodemap is available for the current map.
It walks around to a random corner of the map and sits down. It then says Mossman's voiceline: "I guess you should go with Alyx." Then it screams "Watch out!" and runs into a path and does some kind of blocking attack move. Then it starts the loop again. The intended purpose for this NPC is probably to test NPCs and Nextbots in the game.
People reported that it was flying and clipping through walls, and it could only be removed if the game server was restarted. Though it is currently unconfirmed if those claims are true. The only actually true claims (as of now) is that it can somehow get negative health and never die unless an entity health control tool is used, and also that if someone "drives" it (take control of the NPC) it can somehow clip to the outside of the map almost like you were no-clipping through it. Then she gets stuck there and turns pitch black due to the lighting not existing. She cannot be seen again unless external tools are used.
