Unused Items are items for the game that are not used and hidden Out of Bounds. But these can be seen through glitches in various ways. For example, Medal of Honor: Frontline has hidden Ammo and Health inside the Bunker of the first level. Most of the time these are fully unreachable without the use of a Cheating Device.
Sometimes a level can be cut from the game, and its elements hidden in certain areas or forgotten and not removed. Crash Twinsanity, for instance, has a Beta Water Element that is plain sight, but not noticable.