The Star Citizen First-Person Shooter Combat gameplay will be revolutionary in many ways. Being set in a persistent open world can mean that a firefight can break out at any point in time, in any situation.
Players are also in space or on a space craft or both, which can have interesting implications to the situation. An evil combatant might shut off the artificial gravity generator onboard a space station and effectively change the firefight into a zero gravity situation. Or a space craft that previously had an atmosphere could have a wall blown open and all of that atmosphere get sucked out and perhaps a player along with it.
A back alley brawl between two rival organizations might break out over a failed black market trade. Perhaps that brawl escalates and spills out into the streets of the planetary port that you are landed at.
Who knows, the possibilities are endless.