Mount and Blade: Warband. Not singleplayer, mind you, I've already helped overthrow one kingdom and am well on my way to starting my own, but multiplayer. Everyone else seems to have better hit detection and responsiveness than I do. Of course, I got a little bit better when I realized the combat speed setting also applies in multiplayer, so was in fact moving slower than everyone else. I still suck though, and the fifteen seconds of life followed by five minutes of waiting for the next round to start make me ragequit pretty frequently.