I received an unexpected upgrade on Sabena, 1999, flying from Brussels to ATL. I was in the military and heading to a 6 week school so of course I had my ratty Walmart golf clubs. The agent felt so bad charging extra for the carpy clubs he upgraded me to biz.
I got another upgrade, Doha to Houston on Qatar Airlines just asking if one was available. The agent handed me the biz upgrade and no charge. First and best flight ever on Qatar.