For me, my best two moments are connected, but occurred about a year or two apart from one another.

So, back on the old Guild Site I was a part of a large zombie survival RP set in The Walking Dead universe, but taking place on the West Coast. My character joined about a month after the roleplay actually began, just after the group of survivors had moved from their original safehouse to a new location. He was essentially among the first refugees to join the original, core group. Along the way he had kept a journal, chronicling the events of their rag-tag little faction.

That roleplay lasted for another year or two, dipping occasionally, and losing many of the original cast along the way. By the end, my character had become one of the primary political leaders of the group, had gotten engaged to another survivor and adopted an orphaned boy as their son. But the roleplay was winding down, and needed some sort of a conclusion. Eventually it was decided that the story would end with the vast majority of the characters stranded on the roof of a school while the horde clambered up the stairs, allowing a few others to escape and live another day. We left it at a cliffhanger.

It was revived for about a couple months after that. My character was one of the few to have survived the battle at the school, but he had gotten bitten not a few weeks later. Struggling against the infection, he ran away from the rest of the survivors, holed himself up in a warehouse and began to go insane, writing constantly in the journal. In the end, he succumbed. His death was probably the saddest moment I'd ever written, while also being one of my favorites.

About a month later, the site crashed.

Fast forward a year or so. A few people from the original RP were still around, and we rebooted it for a third installment. I played a new character (obviously). In his possession was another man's journal, a battered old thing he had looted off the body of a walker he found while looting a warehouse. A flashback showed the moment when my new character came across the remnants of my old character and had to end his life yet again. On the bright side, a part of him was able to live on in the journal.