I've begun to use words and expressions while living here that seem to be unique to Korea. Probably the one I use most often is: take a rest. I'm not even aware that I say it, although whenever I do so around a certain American friend, she points out that I'm becoming so Korean.
For the uninitiated, here's a scenario involving the expression:
Me: Wow. I'm really tired!
Colleague: Oh, you should take a rest.
In the States, we take a nap and take a break, but when it comes to resting, well, we just rest (as in: I'm going to rest for awhile.). What a fun yet confusing language!
Wish I could take a rest right now, but alas, a stack of essays awaits me.