A Bygone Era
You probably can't do this in 2017 for public relations reasons, but in Subspace you could have you own .wav file. Subspace players called it the "Kill Macro". You could send it to anyone in the game by selecting them, which was fast and easy to do. SCO is 1v1, so it could just be automatic on kill and you wouldn't even have to select a player to send it too.
It's a shame that you probably can't do this in 2017, there were some great ones. There was a player who would send Fred Flintstone yelling "Yabba-Dabba-Do!!!", another guy played the Star Wars Empire Theme.
I actually didn't use a .wav file. I went by the name "Disco Duck" and had text macros for "Quack!" (I got you good) and "Qua..." (you got me good). Then I almost never spoke in chat on purpose, and people loved me for being almost religious about only "Quacking", haha!
EDIT: I started thinking... you probably can't allow players to choose their own .wav files these days, but the AI pilots could each have a catchphrase they use when they beat you in Fleet Battles.