I keep seeing commercials for an office supply store that advertises an "easy button" to make life easier. This site has a few additional buttons that you might find a use for in your life as well.
The Panic Button has an adhesive back and looks like it could be used for a little fun. I would choose the ESC button for placement but you might know a better place for it on your keyboard.
There is also an Any Key for when your system tells you to "press any key to continue"...this makes it much easier for you to find during those times. With a self-adhesive back, once again, this key can be placed on your keyboard (or a coworkers keyboard when they are not looking) and hear the jokes fly.
Something fun and different to lighten up the mood.