I asked a much newer coworker who was leaving the company what he was making. It was significantly more than me. I've been there for years, and I'm also a veteran, so the company gets a tax break just for employing me. I saw my boss and a team lead and it went like this.
Me: I'd like a raise to $18.25.
Boss: And why is that?
Me: Because [other coworker] was making that.
Boss: Shit. How do you know that? How did this come up?
Me: It came up.
Team lead: Heavy sigh.
Boss: Well, I'm going to have a talk with him. He told you?
Me: I asked.
Boss: You know you're not supposed to talk about pay, right?
Me: I do know that it's illegal for you to tell us we're not allowed to talk about pay.
The boss and team lead are visibly shaken.
Boss: It's illegal?
Me: Yes.
Boss: I'll ask HR about that. I'll see what I can do, buddy. I'll talk to [his boss] and see what she says.
Notice how he wasn't going to give me the raise and thought he could intimidate me and my coworker who is already leaving, and then changed his tune. If I don't get the raise, I'm leaving.