Dark Detectors - Daydream Charm, Patented - Dark magic items - Deathly Hallows - Deathstick, the - Decoy Detonator - Deluminator - diadem of Ravenclaw - diary of Tom Riddle - dishes, cups, and plates - Dom - doors - dragon, model - Dungbomb
Various Dark Detectors are found in the Room of Requirement when it's set up for D.A. meetings. Harry told the others that they shouldn't rely on them too much because they can be fooled (OP18).
Dark magic items
See DARK MAGIC ITEMS.
See DEATHLY HALLOWS.
See ELDER WAND.
Daydream Charm, Patented
This Weasleys' Wizard Wheezes product is packaged in a colourful box with a romantic fantasy scene depicted on it, but we don't know what the item itself looks like. When activated, the user enters a realistic, "virtually undetectable" thirty-minute daydream; "side-effects include vacant expression and minor drooling" (HBP6).
The item requires an incantation to trigger it; eating it isn't referred to, so it has been classified by the Lexicon as a magical item rather than a potion (HBP6).
We don't know how the wizarding patent system works, although it can be applied to spells (e.g. the Horton-Keitch Braking Charm) as well as devices. Since the twins have only been in business formally for about two years (dating this from their receipt of the Triwizard gold from Harry), the patenting process must have worked pretty quickly in this case.
One possible anomaly that may not be quite evident to U.S. readers is why the product is "not for sale to under-sixteens" (HBP6). Sixteen is the age of consent in Muggle Britain - that is, the age at or above which someone's consent to an agreement is considered valid in law (NSOED). In this case, that would mean that the product isn't for sale to anyone who isn't legally competent to consent to the consequences.
It seems a bit odd that a wizarding product would be packed with the age as sixteen rather than seventeen, since seventeen is the age of majority in the wizarding world (the age at which someone is considered an adult). (Granted, the age of consent in many legal systems is lower than the age of majority; that may be the case here.)
This Weasleys' Wizard Wheezes product is a "weird-looking black hooter-type object" that, when dropped, will scurry off and make a loud noise just out of sight. Even when not in use, a Decoy Detonator will attempt to do this, though without setting off a noise (HBP6).
Ron, who wanted to return to Harry and Hermione but could not find them, heard Hermione's voice coming from the Deluminator on Christmas morning - the first time either she or had Harry had spoken his name since his departure. When Ron then clicked the Deluminator, in addition to putting out the lights it made a ball of pulsing bluish light appear outside his window, resembling the light from a Portkey. When the ball of light floated into him - it was hot - it gave him the knowledge he needed to Apparate to their location. It did so again when he failed to make contact and activated it again (DH19).
The diadem was stolen by Helena Ravenclaw in an effort to surpass her mother Rowena Ravenclaw. Helena Ravenclaw then fled to Albania, where the diadem remained hidden in a hollow tree for centuries after her death, until Tom Riddle managed to charm her ghost into revealing its whereabouts (DH31).
diary of Tom Riddle
See DIARY OF TOM RIDDLE.
dishes in the Great Hall
The door to the high security vault in Gringotts would only open when a Gringotts goblin would run his finger down it, causing the door to melt away. If anyone else tried that, they would be sucked through the door and trapped inside the vault (PS5).
The door to the kitchens in Hogwarts is a painting of a bowl of fruit (see). When you tickle the pear, the door giggles and opens (GF21). The Hufflepuff common room is accessed through another still-life nearby (BLC).
See also ACTION FIGURE.
When handled, they leave a person's hands dirty (OP4)