40 Knives is an achievement/trophy in the Call of Duty: World at War Nazi Zombies map Der Riese. To earn it, you must kill 40 zombies with the Bowie Knife.
- The Bowie Knife is a one hit kill up to Round 11, so buy the knife as quickly as possible.
- Avoid standing in easily surroundable areas.
- 40 Knives is also easily obtained during an Insta-Kill on higher rounds, with large numbers of zombies.
- Hellhounds count toward this achievement.