It's interesting to see the differences in companies and their perspective on having fun while at work. For example, back when I worked at Fry's despite being right by the software department and having to listen to Shakira or other crap all day long we weren't allowed to play our own music in the department because it might offend customers? WTF?
At my previous employer we had cube wars (Nerf balls, bean bags, etc). This was frowned upon by most of upper management, so we just did it when they weren't around. Plus the one VP on our floor was usually the person who started it. But, they were picky about you surfing the web, setting your own wallpaper, etc.
On the other hand at my current job I thought they were playing a joke on me (because I'm one of only 2 gamers in the company) when they told me we were getting an Xbox. I was wrong. I just finished hooking up our company purchased XBox 360 Elite to our 50" HP 1080p LCD TV. We are also getting a bumper pool table and a "putting green" in our break room. I spent my lunch laying on a leather couch at work playing Rainbow 6: Vegas. Sweet.
How fun (or not) is your workplace?