People who are REALLY into the game.
Honestly it's they key to an epic game, and the one thing you can't really control.
When I hit the field and see guys properly geared, dressed and ready to lay it down, it's a whole different thing. You start hearing people shouting commands, looking around with energy and enthusiasm. Playing the part, getting into the role.
You get a group of folks like that and you can get stoked playing Nerf.