So, I'd actually consider myself a rat. My only goal is to vacuum up a backpack full of trash barter items and call it a day. I can afford decent ammo, but I don't buy it because I only plan on surviving a fight with a scav. I don't suck at PvP, but I'm not good enough to pose a threat to a seasoned player.
That said, one of the few tricks up my sleeve is psychological warfare: calling them a rat. Any time I've made enough noise for a nearby player to have most likely heard me, I use the "WE GOT A RAT" voiceline. It's all about getting in their heads and lowering their confidence, making myself seem like a bigger
rat threat than I am. How?
If they were trying to stay quiet and were thinking they could sneak up on me, calling them a rat immediately dashes the notion that they have the element of surprise. I know you're there punk, and I'm wearing steel-toe boots.
Using a loud voiceline lets them know I don't care about being heard, and am openly inviting them to come fight me (even though I'm hoping they leave). Confidence, or the faking of it, is key.
Calling them a rat lets them know how little I think of them. Either they're a scav or low-gear player and I've just called them out on it, or it's a chad that would probably ruin my day and he now thinks I'm some tough shit that could give him a run for his money (I can't).
Oftentimes, they'll use a voiceline in return, letting me know their whereabouts. Not always relevant, since I only WE'VE GOT A FUCKIN' RAT when I've already heard someone nearby, but still useful.
Note that using USEC 3 voice is imperative for this technique, as that's the only one with the necessary aggression in his tone.