When Leon is equipped with his Mobster Costume, Leon uses a silver switchblade with some jewels set in it. This knife is a double edge stiletto. Leon, Krauser, and Ada are the only characters to use a knife in The Main Game, and The Mercenaries. In the Mercenaries, Krauser wields his knife; differently, he holds the grip with the blade facing the opposite direction. His knife attack also has a wide range, giving him the advantage of hitting enemies around him.
Ada uses a folding knife. Ada's knife is some rotational lock-in knife where the knife is tucked inside the grip itself, most notably via the model and in one cutscene where Ada grabs her knife, unlocks it and stabs Leon with it in self-defense.
Ada's knife is usable in Separate Ways only in the PS2/PC 2007 Port, and it's not available in the GameCube version due to the apparent lack of Separate Ways, however starting with the Wii and all later versions it is now usable through the whole game modes, including Assignment Ada and The Mercenaries.
A player could hit projectiles away that was thrown at them with just a knife swing (arrows and scythes). This has to be done with perfect timing. When fighting Krauser in his mutated form in both the main game and Separate Ways, the knife does a considerable amount of damage to him. It only takes a handful of hits to defeat him.