I imagine the different possibilities...

• Play in your cube briefly and then hide your gear away when someone comes to investigate -- sneaking into a stairwell works just as well and probably covers more building area.
• Arrange something with your employer to put on a show at lunch -- your coworkers will appreciate something different and think you're cool or finally leave you alone about the fact that you play some form of bagpipes.
• Go out into the parking lot -- Simple!
• Go to a near-by park -- this keeps you from getting into trouble at work and acosted with any complaints.
• Go somewhere that won't cause you to get fired ... this point is rather important.  Oh, and if you work night shift, also take into mind going somewhere that won't disrupt the rest of us sleeping -- although I know you put up with the rest of us when you're sleeping.
• Go somewhere that will cause you to get fired if you want to get out of your job -- I mean, how cool and weird a reason to have gotten fired for playing bagpipes!
• See if you can blend in with coworkers taking a smoke-break -- "Hey, what kind of pipe is that?"
  
• Play somewhere weird that will get you notice but also play somewhere safe (ex. if you're a flagger on a road construction crew, its probably not so safe to play right on the road).
  
• Play for the sake of advertising your skills & services as a piper.
• Play to help further piping and the publics awareness of piping.
• Play for the sake of showing how cool what you do is and to show up that loud-mouthed jerk you work with who snubs you for playing pipes instead of a "normal" instrument.
• Play to see if someone will buy you lunch because -- hey -- free lunch!  Try and disprove the old saying about there being 'no free lunch'.
• Play any kind of pipes (but it has to be of the genre of instrument -- banging on the plumbing in the bathroom doesn't count).
• Play to do something cooler, more distinct and unique than Talk Like A Pirate Day.
• Play for the glory and furthering of piping.  Wait, didn't I say something like that already?
• Play because it's probably more fun than what you're getting paid to do on the clock.
• ...And be sure to play a round of Happy Birthday for BagpiperDon (9/28 -- WOOT!)