Tentacles always get cut
Whether naughty tentacles or Combat Tentacles, these snake-like appendages have several features that make them highly cuttable: 1 They tend to belong to the bad guys, and highly inhuman ones. Finally a chance for the hero to show that his sword can cut something besides inanimate props. 2 They (usually) have no skeleton to stop the blow 3 There is usually more where that came from, especially if the owner has a Healing Factor. That makes them much less dramatic than other limbs but on the other hand you can cut off many in a single scene. In video games the trope is often enforced through Typical Tentacle Tactics.