There were quite a lot of them in numerous games, but recently:
1. Killzone 2: I heard a guy on the mic say "*BURP* this one's for you, baby" before getting sniped in the head. When he spawned again, he was whining.
2. Killzone 2: There was one guy on my team who was owning the entire opposing team. So when they finally gunned him down, nearly 5 people started t-bagging him. At the same time, I lobbed a grenade there, so it killed all of them. The guy on my team was laughing hard when that happened.
3. MGO: It was in TSNE, and I was in spectator mode since I was killed thanks to an idiot teammate of mine. So I see one of my teammates get CQC'ed and stunned. Just as he was about to be stabbed, a grenade came out of nowhere (from the opposing team, of course), and sent both the opponent and my teammate flying off the ledge to their death. Shortly afterwards, another teammate of mine was running away from an opponent. Then an opponent pops out in front of him. As one of them fires, my teammate ducks out of the way, so the opponent killed his teammate instead. Finally, another one of my teammates was being shot at, so he forward rolled off the ledge. However, he was killed as he forward-rolled, so he did a nose dive to the ground. I was laughing for nearly half an hour non-stop.