Boards
Nerf guns
In the office I work in now everyone has a Nerf gun and usually once a day or more, there'll be a few shots fired which sometimes escalates into everyone shooting everyone.
Someone actually got damage to their cornea after one scraped across the front of their eye which buggered their vision for a couple of weeks. The solution? People wearing shades during the fights, so they look even stupider than they did in the first place.