Okay, so... I'm ready to talk about my "bug".
This is something really strange to talk about. I swear I'm not making any of this up.
I don't really know since when , but VERY rarely, sometimes when I die or get a kill, Heavy's "Kiss me" line will play.
Yes, I'm sure. It only triggers when I die or get a kill. It's not a server plugin, this even happens when I'm trying stuff in a listen server in tr_walkway.
I'll just be playing normally, and out of the blue, I'll die and hear "kiss me". And after a while, when I forget about it, I'll kill two people with a rocket and hear "kiss me".
Nobody else can hear it. The weirdest part is that this also happens IN MY LAPTOP.
The only explanation I can think of is having caught some sort of nasty "kiss me" STD from installing a HUD or downloading content from a server sometime, and somehow did the same or copied over the responsible files in my laptop.

I really want to hear that I'm not the only one, that this is a thing that happens and that someone figured out why this exists. I beg you all.

it's your killstreak thing

everytime you die and you got a killstreak it saves it in a killstreak text file in your demos folder and makes that noise

happened to me so i figured it out.

you are welcome