Just like the bullies you knew in elementary school, these people use intimidation and threats in an attempt to demean you and build themselves up in the process. To stop a bully in his tracks, remain calm, but don't be a wimp. Instead of hiding out in the photocopy room after a run-in with the company bully, stand your ground. Please stop by my desk after you've calmed down. Then walk away.
Nothing is more infuriating to a bully than someone who refuses to listen.
By walking away you've asserted your position, and you've let the bully know you refuse to be intimidated by him. And don't be afraid to confront a bully in public. Most bullies spread their nastiness around, so others are bound to support you if you call a bully on the spot. Back Stabbers Back stabbers are just as vicious as bullies, but they shy away from confrontation. If you find out someone in your office is talking about you behind your back, the first thing to do is verify if it's true.