Blade Master
Defeat 10 Enemies while holding a weapon

There is no point in the game where it will teach or force you to do this particular skill. You must do so on your own, so please ensure to do so before the end of the game. Once the game has been beaten, enemies tend to stop spawning. This can be done with the guitar or the sausage.

There is no one place this has to be done at, but I recommend the Shifu level - Village. At the start of level you will be given the chance to pick up a guitar from the first building on the right. Do so and get all the kills you can with it. The 2 wolves in the huts firing guns cannot be defeated with it. After all of the enemies are dead, let the 2 shooting wolves kill you. You will re-spawn in town from the beginning of scene, but you also keep your kill count. Grab the guitar once again, then kill a few more enemies and the trophy will pop.