Wand of Change - Enables user to find enough change to make a local phone call. In pennies. Wand does not take into account distance between the user and the change.
Might I venture that you do not play/GM in a true multi-GM campaign? 
This sort of inventive cruelty is fine (and to be encouraged) provided you know completely what tools and abilities the party have, but… I have GMed DragonQuest these past 16 odd years in a multi-GM campaign (up to a dozen GMs and 70-odd players at its height) and learned well that vast blocks of silver and the like may sound fun in theory, right up until one of the players pulls out their handy dandy spell/wand/bag/hat of shrinking and/or holding enormously heavy objects, unleashing rampant inflation on the local economy and exposing one to the ire of the other GMs. 
Sure, you try and check through all their stuff before the game, but with PCs who’ve been around (in some cases) upwards of 15 years accumulating hoards of loot it’s too much to figure out all of the evil plans they might concoct, and worse, the synergies they may find between their various weird and wonderful abilities.
I’m with **2trew]/b] on this, many of these “useless” items have excellent albeit limited uses in the hand of sufficiently devious players.
And old RPG The Fantasy Trip had a similar substance, but it came in two bottles, parts A & B rather like epoxy, only more liquid. Mix a dop of each (carefully!) and poof a baseball sized cloud of gas that ate anything – great for locked doors.
'Course, safest way to transport the fiendish stuff was for two PCs each to carry one part – unlike the hapless PC in a game of a GM friend who got hit with a telekinesis type effect, thrown down a corridor and hit the end wall backpack first wherein were both A & B bottles. POOOOF
Another player, in a game I GMed had the misfortune to be a passenger on a ship where the crew mutinied. Annoyed by the lookout with the bow in the crows-nest he fashioned a jury-rigged bolas from a length of rope and A & B bottles and launched it at the mast resulting in 10 feet of the main mast vapourising and the remaining length plunging through the ship.
One for the Harry Potter fans:
The Mirror of Serutan
The Hat of Believing – The wearer of The Hat of Believing has the ability to believe in it. This effect is continuous as long as the wearer believes in it. The wearer of the hat can also run, jog, or take a casual stroll along the beach in it. The hat need not be worn in order to believe on it, near it, about it, or under it. However, believing through it will produce no observable effect.
Linna Inverse’s Wand Of Dragon Slave–has the power to end the campaign.
Apollyon–I know, I know. One campaign, a guy got ahold of a sword that could transform itsself into any other kind of magic sword, for one day only. Then, it became non-magical.
He asked for He-Man’s Sword of Greyskull. :smack: I threw my can of Coke at him.
OTOH, if you’re playing NetHack and find a potion of Holy Water…
This made me think of the Tampon of Many Skills…
You know, with it you can ride a horse, go canoeing, fish, go dancing…
I know many, many people who could use this 
Wand of Enemy Detection -5: Detects enemys who are less than one foot away. Doen’t work if enemy is hidden by walls, bushs, ect.
This would be quite useful - never know when you need tactical nuclear -level destruction. Or it can end campaigns that just drag on.
Scroll of Dramidj’s Instant Death: causes Dramidj, whereever, and whoever he is, to die instantaneously, no saving throw.
– From an old Dragon April fools issue.
Potion of language detection - While this potion lasts, the imbiber is able to tell whether anyone speaking to him/her is using a language or not.
That item would be very useful in some of the campaigns I have played, furryman. We had a lot of interparty intrigue and being able to find out who was plotting against you at any given time would have saved a lot of grief and actually got the party into the adventure rather than the over wrought attempts at backstabbing to steal your good loot.
Wand of Blunder: To all tests, appears exactly like a Wand of Wonder. However, when the wand is used, it only mimics the silly, useless aspects of the Wand of Wonder, such as making flowers appear on the target’s head.
Mordenkainen’s Steak Knife: +5 keen vorpal wounding vs. porterhouse.
Dust in the Wind: When this dust is tossed into the air, all creatures within 30’ feel a momentary sense of sadness and futility.
Fist of the North Star: When the wearer of this glove punches someone, the target flashes between its normal appearance and a black-and-white image of a skeleton, whether or not the target actually has a skeleton.
Figurine of Wondrous Power: Iron Butterfly: When activated, the user speaks in a deeply resonant and musical, but mysterious, language, which resists all attempts at translation.
Jeltz’s Bablefish Amulet - makes everyone sound like they’re reading Vogon poetry.
Synfeldt’s spell of nothing – Causes the caster and anybody within 30’ to talk for 20 minutes about nothing of any significance, often repeating the same word several times in a row. This talk can take place while battling, and the opponents will be included. No saving throw.
Billshat’s amulet of emoting – Causes the wearer to speak in an overly dramatic fashion. Has the occasional side effect of causing the wearer’s hair to look fake.
Wand of poop – It’s a wand. Made of poop.
Quoth milo minderbinder:
That’s OK, just cover it in chocolate and sell it in the mess halls.
That said…
Potion of Dilution: Dilutes any liquid by an amount equal to the volume of the potion.
Amulet of the Prime Material Plane: On uttering the command word, wearer is instantly transported to the nearest spot on the Prime Material Plane. Note that since magic functions differently on different planes, this amulet does not function when on any plane other than the Prime Material.
Trinket of Nystill’s Mystic Aura: Can expend a charge to put a false aura on any other trinket, causing it to appear to be a Trinket of Nystill’s Mystic Aura.
Ever-Full Waterskin: This magical waterskin is always completely full of water. Note that it’s impossible to get any water out of it, since then it wouldn’t be full any more.
Potion of Extinct Animal Repulsion: Well, you don’t see any extinct animals around here, do you? See, it works! Note, of course, that any animal which becomes un-extinct is no longer affected by the potion.
Orb of Nothingness: Behaves exactly as though it weren’t there.
Wand of Paradox: A character may activate this wand only after they have successfully activated this wand.
Great Sword of Slaughter: +999 damage vs. thumb-sized insects. Due to its great size, this sword may only be swung once per minute.
Potion of Relief: After imbibing this potion, the drinker is incapable of misspelling R-O-L-A-I-D-S.
Knife of Butterslaying: This magically-warmed knife cuts through butter like a hot knife through. . .butter.
Cauldron of Doubling: Double the quantity of any potion! Simply pour the potion into the cauldron and add the appropriate reagent. The appropriate reagent is another potion of the same kind and quantity.