The day I just clicked with flying my Orca. I'd been struggling to win any fights, be it in a GB, bomber or fighter, when suddenly I took out 4 bombers solo, and they weren't nubs either. I started looking for fights where I was outnumbered, and outgunned. Eventually people started to figure out how to combat a pulse/razor gunboat and the playing field levelled, but those early days were just an awesome feeling.
Edit: Also, the feeling when my Fortunatus Wright story won the writing competition. The winning wasn't as special as realising that people were reading the story and enjoying it.