i would start my own faction.. my goals and personality dont really align with any of the preset factions and if society is reset to 0, why be a lapdog thats forced to do tricks and only sometime fed scraps from larger organizations table?
Arroyo after Fallout 2 or MW Brotherhood, maybe NCR Rangers.
I'll probably hate myself later for this, but I think I'd join up with the Paradise Falls slavers. Gotta make a living somehow, and it'd more or less keep me from ending up in the pens with the meat, long as I don't pissed Eulogy Jones off.
If you want be a Slaver chose Metzger's Salvers Guild, the Slavers at Paradise Falls looks like raiders.