Knife

From the Castlevania Wiki, the Castlevania wiki

"Knife" is often another word for Dagger, the subtle difference being that it is either one of many ways used to detail and classify damage inflicted, or simply as an unthrown, equippable weapon used in close combat.

For example, in Lament of Innocence, it is used to describe the type of damage that is dealt by a knife.

In the other case, the most notable use of the knife as an equipped primary weapon is that of Grant DaNasty's usage of said item. His mastery over the weapon was such that he performed Iaijutsu-style cuts on enemies while falling from a ceiling where he was perched.

Soma Cruz and Jonathan Morris are also known for being able to equip weapons of this type, among many other assortments of weapons.