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.
Tootsie is a chocolate candy that has been manufactured in the United States since 1896. The candy has qualities similar to both caramels and taffy without being exactly either type, and does not melt while being transported during hot summer months and another is Pepero which is a cookie stick, dipped in compound chocolate, manufactured by Lotte Confectionery in South Korea since 1983.