Tower of Doom/Other Items

Boot
These are valueless, except to offer in trade to monsters with low intelligence (e.g. the Giant Rat). Color doesn't appear to matter.

Food
Food is always brown, and appears to be a piece of meat on the bone. Eating food restores Life Force to a full 255 points, and also increases Stamina.

In Tower of Doom, food -- and the lack thereof -- are probably the single biggest issue in survival. The player's Life Force is constantly draining with every heartbeat, and can be further depleted by Life Eater traps. When Life Force reaches zero, the player's heartbeat will change to a sharp thud, and the player will lose one unit of HP (or 1/4 of a Shield symbol) with every beat, killing the character within seconds, or a few minutes at most. Thus, without spare food, even an extremely powerful character can quickly end up in mortal peril. (The Grail and Rosary can also restore Life Force, but both items are rare.)

That said, there's no advantage to eating any sooner than is absolutely necessary, and one should usually ignore both of the game's warning messages ("LIFE FORCE IS LOW" and "LIFE FORCE IS CRITICAL"). Instead, the player should generally wait to eat until the heartbeat changes (approximately 16 beats after the "LIFE FORCE IS CRITICAL" message) and the player's HP begins to drain. In randomly generated dungeons, one will frequently go several levels without encountering any food, so getting the most out of every piece of nourishment is crucial.

Keys
Keys are used to bypass traps, and can be extremely useful (especially the Magenta Key). However, you have to have the key in hand, i.e. in place of a weapon, for it to be effective.