Mine's not a story of great heroics or raucous humor, just my roleplaying moment I look back on most fondly out of my many years of play. We were playing a RIFTS campaign and were about 10 weeks into it. Us PCs were a mercenary group doing a job for a mysterious client (aren't they all?) and as well as us we had a small convoy of vehicles to travel around in including some NPC assistants. The GM had originally included the NPCs to generally make things easier for us and take care of arbitrary tasks but we did a lot of roleplaying with them and they each developed personalities that grew on us and it had begun to feel like a family. Returning from an 'away mission' back to our troupe one day we found that one of the drivers had stolen a 'package' we'd previously recovered for our client and fled with it. As betrayed as we felt, it wasn't a patch on what we felt when we discovered the body of Red, the technician Lizardwoman, outside the camp. When she spotted the driver slinking away and approached him he pulled a gun and fired, killing her. We'd grown fond of her, she was always helpful and a little naive; she was the little sister of the company. We, as players every bit as much as characters, were genuinely sad at this plot twist. It was the end of the session but we all stayed an extra half hour that night to roleplay a proper burial for her. We each went around the table saying a few words for her, or reciting some impromptu anecdote about her. It was a truly beautiful moment and always makes me smile when I think back on it.