Thomas Moore

Thomas Moore is the vocal abolitionist and proponent of opening Vault City to Outsider that preaches his beliefs in downtown VC area. His unkempt hair and scruffy beard, contrast with his clothes that look clean and well-cared for. Most Citizens just ignore him, preferring not to talk to someone obviously crazy. Interestingly, Moore was not born a vault citizen but managed to gain citizenship presumably by passing the arduous citizenship test to gain access to Vault 8 and citizenship. He became a Vault City citizen in 2240.

In reality, Thomas Moore is an undercover NCR agent gathering intelligence on Vault City and smuggling its technology outside. His contact is John Bishop of New Reno, to whom the Chosen One can deliver a briefcase containing Moore's intel and a piece of VC tech (Super Stimpaks most likely).

Moore can be ratted out to Lynette, which ends up with him being permanently banished from the city and revoking of his citizenship.

Behind the scenes
He is often believed to be a throwback to either Sir Thomas More or Michael Moore, but in fact he's just a reference to Chad Moore, one of the Fallout 2 developers.