You can also butcher with other sharp-edged tools like [[carving knife]], [[hatchet]], [[pickaxe]], [[shovel]], [[sickle]], [[stone chisel]] or [[sword]], but using a butchering knife gives more items.
For optimal skillgain butcher an animal corpse with a high quality butchering knife initially so that you have a higher chance at getting a full butcher or more butchering products. Then, use a low quality butchering knife with a high [[CoC]] to filet the creature's meat.
Note: Butchering human corpses makes your [[alignment]] drop by 1 and does not give any butchering skill.