combat knife
A knife designed with hard use in mind, often used not only for fighting but also for utility purposes. Usually built with a full-tang construction and a durable, stainless steel. The handle can consist of a number of materials, including leather, plastic or a composite. May or may not have serrations.
Few type of bayonets do also function as standalone combat knife, such as the M9 bayonet (post #1684456).
See also
This tag implicates knife and weapon (learn more).