According to Tattoo Joy, a knife or dagger symbolizes confrontation, justice, war or death. Many individuals get tattoos just for aesthetic reasons, so not all knife tattoos have the same meaning, or any meaning at all.
The knife tattoo represents a willingness to fight until the very end. In the ancient days, the knife or dagger was the last option when other weapons were not available.
The meaning of a knife tattoo may change if there is another object included such as a skull, rose, heart or snake. The knife is common in many military tattoos, as well as seals and crests.