Quick answer: Euro-style round-pin plugs
Long answer: The official Korean plug is 4.8 mm in diameter whereas the Euro-plug is 4.0 mm. This means you *could* encounter some "loose connections" unless you use the European *grounded* plug which *is* 4.8 mm also. Apple users get both a Euro plug and a Korean plug in the world-wide plug kit for the white power bricks. Springloaded adapters such as the Sascom and Gocom are good alternatives.
I am shocked that the IETF didn't rewire downtown Seoul to accommodate our conference! The next thing we'll hear is that our TDMA phones won't work. Or that they don't have TGI Friday's within easy walking distance. :-)