Mine- I ran a road 5k this past summer and was leading the second group in sixth place until one of the runners in my group surged and got around ~100 meters ahead. I was running PR pace however and kept him in sight, slowly catching up.
In the final straightaway I sprinted past him with everything I had left and beat him by a few seconds for sixth place in 16:24. that was a 34-second pr for me. Maybe not my absolute best race ever but probably my the one I'm proud of most. The 1st/2nd place guys were well under 15 minutes though so I'm working hard to get to their level now.