I live in Seoul. I always see things that I think would do super well back home, but for whatever reason (stricter laws, smaller population, less foot traffic, etc) they just wouldn't work. Anyhow, these are some.
- Video Game/Movie Rooms - Rent a private room with a giant HDTV, surround sound, and super-comfortable seating. - Play Wii/PS3 with your friends or watch a DVD/BluRay. - Free snacks (crappy soda, popcorn, etc.)
- Cat/Dog/Animal Cafes - Overpriced coffee shop where you can play with kittens/puppies.
- Errand Boys - Delivery service for whatever you want. Is there a restaurant you want to eat from that doesn't deliver? No problem. Need a book bought and delivered in the next hour? Sure. Need your light changed? They'll be right over.
- Grocery Delivery Service - Basically for people without cars. If you shop in store, but have too much to carry home, they'll deliver it at a specified time the same day (free of charge if you order enough).
- Board Game Cafes/Bars - As mentioned earlier. Pretty much the same thing. In the cafes, you pay by the hour. In the bars, if you buy a drink you can just play for free, but the games are usually much more limited.
- Bagged (Alcoholic) Drinks - The bar equivalent of a taco truck. They setup in nightlife areas with lots of foot traffic on the weekends. Some are simple and only sell a small variety of cocktails. Some are fully stocked bars.