The butter knife is a emergency starting weapon which can be found in most houses. Out of all the basic cutlery (butter knife, fork, spoon), the butter knife is the only basic cutlery that can do the insta-kill jaw stab (if timed right). However with every hit on a zombie guarenteeing item condition falling by 1, and having a max of 5, it means you only get 5 hits with the knife before it breaks.
The butter knife is a single attack weapon, meaning it can only concentrate on one zombie at a time, attacking two at a time is risky as only one zombie will be stopped per hit and the other could get in close enough to damage the character.
One if the benefits of the butter knife is that it is plentiful in the game world and is quite light. The butter knife cannot be repaired.