I'm guessing this is what people have been using to override the game-end fanfares and such?
Hmm, OK, the files in question are actually called game_sounds_*.txt and are divided up by type. Easy enough to fiddle with. Looks like I might be able to mess with impact sounds as well, good to know... I also happened across a file called surfaceproperties_manifest, and it got me to wondering whether it would be possible to override the default surface impact decals as well somehow.