I think this is probably the best post that gives suggestions. Seriously, you should know your dad's hobbies, so get him something that he likes.Ilikemilkshake said:Get him some kind of fancy alcohol, maybe an expensive bottle of whiskey, wine or champagne.
If he's not into alcohol then maybe get him something relating to a hobby he has, if he's into fishing, golf or even DIY or something there's probably something in that area he could be looking for.
EDIT: ooh you could maybe even get him something interesting from south korea aswell (not sure what though)
My dad is a huge Sci-Fi buff, so my brother and sister and I usually chip in to get him a boxed DVD set of one of his favorite shows that doesn't air that often (Original Star Trek, Original Twilight Zone, Sliders stuff like that).
Pick a hobby and get him something related to it, even if he doesn't like/need it, he's your dad and will pretend to like it anyway.