You would go 2nd. Every turn your opponent took, you would counter that by making it equal a total of 4 for that round. Ex: He shoots 1, you shoot 3..he shoots 2, you shoot 2..he shoots 3, you shoot 1. With this, your 2nd to last turn will end on 96. He can no longer win with shooting 1, 2, or 3...knowing he can't win at this point, and knowing once his turn is over that you will win..he may choose to turn the gun on you instead claiming you to be a bonus target. So, even though this method ensures you a victory..when playing competitive games involving deadly weapons, sometimes it might just be better to take the loss of the game rather than risk the loss of your life.. :s

Edit: Didn't read any of the responses before posting..it looks like spark got it right away, but it was definitely more fun trying to solve it myself!