Several times throughout the games, the PC is readily identified by NPCs as a Vault Hunter without so much as a word between them before-hand. Vault Hunters are also generally treated as if they were somehow superior to your average adventurer. The latter is further reinforced in the trailer for the new Telltale Games series, where Marcus tells a couple aspiring adventurers that they'll only get themselves killed in whatever they are trying to do because they are not Vault Hunters.
Vault Hunters seem to come from all walks of life - especially the DLC characters. So far, here's who we've got.
- Brick (Berzerker): Large and in charge, he came to Pandora to find his missing sister.
- Lilith (Siren): I can't find much in the way of specifics on her background in a cursory glance, but apparently there's a geek side to her as we discover in Tiny Tina's expansion.
- Mordecai (Hunter): Professional sharpshooter since he was 17. Has a real attachment to his pet bird-of-prey, Bloodwing, which I'm not sure was ever really explained.
- Roland (Solder): Again, can't find anything in a quick wiki glance, but he's obviously got some military background.
- Axton (Commando): Former Dahl military. Came to Pandora seeking fame, fortune, and combat.
- Maya (Siren): Raised and exploited by the Order of the Impending Storm, Maya has come to Pandora in search of knowledge about her background as a Siren.
- Salvador (Gunzerker): A freedom fighter, native to Pandora, who found out about the Vault while interrogating a Hyperion soldier who had come to take over his hometown.
- Zer0 (Assassin): Professional assassin with an overall mysterious past. We don't even know for sure that he's human.
- Gaige (Mechromancer): A child prodigy who was expelled from school due to an incident involving her latest creation, Deathtrap. While running away from home, she stowed away on the same train that carried Roland, Axton, Maya, Salvador, and Zer0 to Windshear Waste.
- Krieg (Psycho): Krieg is, well... a Psycho. With a sort-of stalker-y crush on Maya. Yeah, I think that's about it.
The only thing any of these people seem to have in common is that, at one point or another, they decided that hunting for the Vault seems like something they need to do with their life. So, what is it about Vault Hunters that really sets them apart? What is it that makes them stick out? What keeps everyone from assuming that anyone can be a Vault Hunter?