[quote=Captain Jenno]
Red Dead Redemption is a hell of a lot of fun in a posse. You claim a territory, and then shoot anyone with the quads to try and enter it, or you mount an invasion on another group that's already doing it. Killtastic.
[/quote]

I'm pretty sure they have something like this in GTAV too. I haven't tested it yet, but in the menus there's an "Enter Crew Session" option, or something like that. My guess is it puts you and your gang (modern posse) into a map that has other crews (GTAV's name for clans) in it. Viola. Gang wars.
And I gotta say, nothing against RDR, but shooting an Uzi from the window of my mustang or 1980s Camaro and blowing the tires of my target at 80+ mph; is way cooler than firing revolvers and lever actions from horses.
Just my opinion.