To make things more interesting, I used a timer in conjunction with the scoreboard. I would move the pen to my side, the center, or the students' side of the scoreboard. I wouldn't mark a point until the timer rang. Whichever side of the scoreboard the pen was on at the time the timer rang got the point. If the pen was in the middle, no one got the point. At times, I would pull out a second or even a third pen (never more than three), and shuffle them around the three different positions so that up to three points could be at stake for the next "ding" of the timer.
Regarding the timer: I started out setting it for 3 minutes, then 4, then I stopped telling students what I set it for. They had no idea when the timer might ring. I never set it for more than 10 minutes.
The effect: renewed enthusiasm around the scoreboard.