Mount & Blade: Warband

Some weapons while appearing as a blunt weapon and showing a blunt weapon icon after you kill someone don't count towards this achievement. The war hammer for instance doesn't count but maces and morningstars do. I found foot combat too be much more difficult with maces then swords from the low damage and slow swing so I recommend you ride on a horse and bash somebody on foot while you ride by. If you connect at a fast speed you should almost always get a 1 hit kill.