I had an idea for a magic item over the weekend. I can not in any way claim much creativity for it, as you'll see. The flavor of this item should be different between OSR and D20, so I'm providing both versions. Needless to say, if you like one version over the other, don't let my arbitrary preconceptions get in your way of your game.
Pearls of Portal, Swords&Wizardry/OSG Edition
The Pearls of Portal are a matched set of flawless but otherwise unremarkable pearls, often stored together in a small felt pouch. To use the pearls, first touch them together, then place (or throw) one of them to another location no more than 360 feet away. While touching the pearl you still have, speak the command phrase ("the cake is a lie") and you will instantly be transported to the other pearl. Transportation works in both directions, and includes any items you are carrying and up to two friends with whom you are holding hands. The pearl does not teleport with you, and if you were holding it, drops to the ground where you were standing.
You may use the pearls to teleport 3 times per day, after which the pearls must be reunited and exposed to moonlight for at least an hour before they can be used again.
Pearls of Portal, D20 "High Magic" Edition
Pearls of Portal are a matched pair of flawless pearls with a limited dweomer placed on them. To use the pearls, touch them together, then leave (or throw, etc.) one pearl wherever you wish. To activate the pearls, hold the pearl in one hand and speak the command phrase ("the cake is a lie"), and you and anyone else holding onto the hand with the pearl will be instantly teleported to the other pearl. Both pearls are consumed by this action. The pearls have a maximum range of 100 feet, and cost 1000gp.
Essentially these are a Dimension Door spell (Wiz4) crafted into a wonderous item that uses one of a pair of pearls as the destination. The S&W version is a permanent item that needs a "ritual" to recharge, the d20 version is more like a scroll or potion, and is priced accordingly. Players will hopefully come up with clever ways to place the target pearl (slings, henchmen, monsters who believe they found a treasure, etc.) and in the case of the S&W version, will hopefully be equally inventive about how they plan to retrieve the pearl(s) once they have used them. (Remember, the pearls do not transport themselves - someone has to go get them.)