Sacred head of the Vault Dweller

The Talking Head is a Fallout 2 special encounter. You can "meet" him in the Wastelands near Arroyo (or NCR, maybe anywhere in the map), and he is actually a talking version of the big stone head of Vault Dweller in the Arroyo Village Center. If you talk to him he says, that you are not the Chosen one, and if you pluck up the time and energy to tell him you are for about a thousand times (actually your Character gets the clue pretty quick so like 5 repeats will do) you get a Monument Chunk as a reward.