Gotcha!

One of the classes I taught recently involved some English "slang". So I was asked to come up with some slang that people might actually say. So I put together a short list of stuff, which may not be popular slang, but things that I might say. My JTE had me add "gotcha" to the list. I told her that people don't usually say "gotcha", but she thought the students would get a kick out of the unusual sound. Which they did.

Cut to today...
I'm going over lesson plans with this teacher, and to let her know I understand what she wants me to do, what do I say? "Gotcha!" of course. She stops, looks at me and says, "See! You do say gotcha!". I guess I do here...

Does anyone actually say "gotcha" outside of the context of teaching Junior High English in Japan? I can't remember anymore.