So, here's a thought. Have fun by utlizing the heck out of YouTube (for videos), Grooveshark (for music), and Hark (for movie lines). It's free. And it makes people laugh.
Here's what I mean.
1. People occasionally sneeze in the office. And when they do, someone usually says to them: "GOD BLESS YOU!" At which point, I respond by playing the following video.
2. Or on Friday's, I love to bump this beat super loud.
3. Or if a sale is made, I like bumping this.
4. Or sometimes I just bust out the god damn Christmas tunes in August or March.
You get the idea. Someone at your company should be responsible for fun! In fact, everyone should! Do everyone in the office a favor and bust out some funniness every once and a smileeee.