I'd recommend some Lindt chocolates for sure. Last time I was preparing to be in Korea I bought probably $100 worth of Lindt chocolates to bring as gifts for meeting people. The chocolates were a big hit with my gf's friends, coworkers, and family. The truffles are amazing and everyone loves them. Also, even though I don't like it, the white chocolate/coconut bars were a big hit. I didn't see any Lindt chocolates in Korea, although I'm sure you can get them somewhere, but I think they're pretty safe and most people haven't had them.