I'm not big on single-player games, but I do have lots of moments from when I played competitively for 4 years... honestly some of my fondest memories. I had some of them recorded but most of the ones I uploaded where ones where I screwed up (and for some of them, my then-teammates now-friends still won't let me live them down).
Most memorable for me though was this golden cap round at Rewind II LAN in 2018:
We played the full match with our opponent team and ended the timer on a 4-4 score, which meant we had to play a tie breaker "golden cap" round (basically, first to score wins the match). This went on for 25 minutes of back and forth with neither of us being able to score. We literally had the entire arena standing behind us by the end of it because our match was holding up the scheduling for the next round of matches
The whole event was amazing and I fully understood why so many competitive scenes cherish being able to play in a LAN setting... It's a completely different experience when you can get up, walk fifty feet and shake hands with the dude you just spent 30 minutes trying to erase from existence.