I used to get lots of good ones back in the PS3/360 days. Nothing anymore since I disabled messages from non-friends after all that PS4 messaging account shit happened a while back.
Stuff I remember that I don't have any replays or screenshots from:
-Played a guy in Tekken Tag Tournament 2 and won. He sent me some generic rage message and I responded with a variation on the Raul Julia classic Street Fighter The Movie line "what was the greatest match of your life was just Saturday for me." By chance I ended up getting matched up with him again soon after. He had his mic on and kept screaming "JUST SATURDAY??! JUST SATURDAY HUH MOTHERFUCKER!!!!" I was cracking up laughing and still beat him again.
-Played a Balrog player in Super Street Fighter IV as Chun-Li. In that game, her jumping straight-up roundhouse was pretty effective against 'Rogs trying to get in. For whatever reason, this player just could not get around this, so I just kept jumping straight up and pressing HK and beat him for most of the match. He started shit-talking and I plugged in my mic, then just went "U MAD U MAD U MAD U MAD U MAD" while continuing to keep jumping up until he went quiet, took the loss, and declined the rematch. I used to have this replay saved on my 360 and wish so bad that I had a way to record the audio from the mic chatter back then.