Sometimes you have to get up and have a little fun. And very little is more fun than starting an in-office battle. One of our favorite toys is the USB Rocket Launcher from Think Geek. Plug it into your computer via an available USB port and use the included software to aim and launch the foam projectiles up to 19 feet. If your co-workers start stockpiling NERF guns, well, then good luck.
USB Rocket Launcher