The Real Laser Tag
My idea is simple but, imo, funny. Have the gang have an all out laser tag war with running, diving, obstacles, the works, in a padded arena or outdoors. But each harness is connected to one of those flat tasers (the kind that looks almost like brass knuckles) pushed in their backs, or chest, or crotch (or all three if you prefer, each one connected to a different sensor: back shot is back shock, front shot is chest shock, head shots are crotch shocks). When you get shot you get shocked. It would make for very funny mid-air shots and possibly guys going down mid-stride.
You could also add mirrors to the arena or small gauntlet mirrors to provide for around the corner shots and the possibility of friendly fire or shooting yourself with a deflect.