The most common type of WUS is the former partier. He's either a little or lot past his hardest partying days. Usually all his old buddies are now married off and have better, more fulfilling ways to spend a Tuesday evening. But back in the day he partied with the best and he has a million stories to tell, from the funny to the embarrassing and everything in between.
Some were small time stars, and these tend to be the most annoying. Examples of this type of WUS include the high school football king and the guy who starred in that local commercial once upon a time. If your bar is home to a full-on WUS, such as an ex-B actor, find a new watering hole. This guy expects special treatment and after a few drinks may actually start fights with anyone that doesn't recognize him from his glory days speaking three lines in a failed sci-fi series.
There's generally no need to avoid the more common WUS varieties. They are usually nice guys. They are just lonely and looking for a conversational partner, but they won't force you to lend them an ear. If one does get a bit annoying, just walk away. WUS butts tend to be permanently glued to the bar stool since they are beyond the days of putting any effort into anything.