According to Gamebanana and the huds.tf backup, it seems like the Quake 3 hitsound is probably the most popular hitsound. I'm trying it out and like it, but I'm not sure what killsound would go well with it

Hitsound: hl1 scientist screaming STAHP and other hurt responses

Killsound: Old Roblox OOF

hitsound: Hooty from The Owl House chocking.

killsound: that one Vinny Vinesauce "death noise" {the one from the Bloodborne PSX video.}

Open Fortress default hit and kill sound (I believe that is from quake 3)