About 5 years ago, while we were waiting for our passengers to show up, I noticed a new Cirrus SR22 out on the ramp. I needed something to do so I wandered over to take a look at it. As I walked over, I noticed that something was amiss - the nose wheel pant was broken and the propeller had "fuzzy" tips. I asked the line guy what the deal was. Evidently, the pilot had taken off from some airport and had landed there for fuel. Apparently, he didn't remove the towbar prior to taking off and didn't discover his "mistake" until after he had landed and shutdown. You have to ask yourself how could you not tell something was amiss? How do you taxi a Cirrus with the towbar attached? Even in a Baron, that towbar would certainly make itself known by feed back through the rudder pedals. Are we brain dead? News Flash!!! If something doesn't seem quite right, it probably isn't.
Over the years, I've developed a habit that I call the last chance walk-around. Simply put, I never climb into an airplane without walking completely around it first. (This is even if I have just completed the normal pre-flight inspection.) You'd be surprised at the things I've found over the years. Some days it can be a couple of hours between the preflight and when the passengers finally show up. Things can and do happen in the meantime. This practice has kept me from embarrassing myself on more than one occasion.