Well, here's the most recent riddle that I used - which is a while ago now!I have used them less than thst. L much prefer the blue delving to be in-game mysteries and the like.
The last riddle session I was in was three weeks ago. One of them hinged on the english spelling and pronunciation of a word, so it did not even cover the scope of our own real world, much less have a "in character in a fantasy world tie." So its answer definitely required leaving character.
And, it was not one that seemed uncommon as rpg riddles go.
[/sblock]the sphinx then came out, and told them that they must answer a riddle before they could pass further into the Mausoleum. I had mixed together abilities from a MM and MM2 sphinx, so they could either choose between accepting the challenge but suffering a debuff until answering it; or rejecting the challenge but granting the sphinx a power up. They chose to accept.
I wrote the riddle a few weeks ago on the train:
In the green garden, a sapling grows,
In time the tree dies, a seed remains.
In the grim garden shall that seed be sown,
Among the black poplars a new tree, a new name:
Shade shall it cast,
Appropriately enough, it was the player of the ridiculously zealous paladin of the Raven Queen who first conjectured that the subject of the riddle was the Raven Queen herself - first her mortal life, than her life after death in which she took on a new name ("the Raven Queen") and took control of the Shadowfell and death, of winter, and of fate.
When the players had reached agreement on this, they offered their answer. The sphinx accepted it, but insisted that they also tell him whose pride will be cured. After generic answers ("everyone dies"), which did not really satisfy the sphinx, the fighter/cleric answered "Us". The sphinx replied "Well, yes, you," and this was the clue for the player of the invoker/wizard, who answered "The gods" - because the fighter/cleric is now God of Jailing, Pain and Torture (having taken up Torog's portfolio). The sphinx then allowed them to pass down the stairs to the principal room, to venerate the dead queen.
Before that I used a riddle from a 4e module, though in my campaign it was located in a different fictional context:
[/sblock]The invoker/wizard translated the supernal on the altar that announced that it contained the Ebon Flame. He prepared Object Reading (taking an hour) while the other PCs studied the sculptures and improvised some defences from the rubble where the floor had broken up. He then placed his hands into the marked slot and released his Object Reading. He learned that the altar had been made by Moradin and Pelor; that the Ebon Flame was within it; and that he was the first to touch it since it had been built. The altar itself spoke a riddle in Supernal (again from E1) - in summary form, what is the formless, colourless thing that moves the gods and causes victims of those who ignore it?
I was impressed that within five minutes or so of discussion the players had narrowed their options to Justice or Compassion/Benevolence. (Hope had also been canvassed but rule out as too non-specific; the contribution of the tiefling paladin of the Raven Queen, as played by his player, was to comment that this seemed to be about one of those good ideals rather than something like pride or revenge, and therefore the others could work it out.) The consensus seemed to be "Compassion", but the word had to be spoken in Supernal by the invoker/wizard, and he refused to place Compassion before Justice (he serves Erathis, Ioun, Bane, Vecna, Levistus, the Raven Queen, and Pelor only rather secondarily). Speaking the word "Justice" the altar blasted him with a crit for 77 points of damage, back into the angel of desolation where he took a bit more damage and had to be healed up before having another go. He then reluctantly spoke the word Compassion, and the altar opened up revealing the Ebon Flame - from which the form of Miska the Wolf Spider immediately burst forth (stats attached below).
I can't remember the third, which was early in paragon tier. I believe I took it from a riddle book, but made sure it was not anachronistic.
Anyway, I hope the two actual play examples illustrate why I don't think that riddles have to involve breaking character or shifting the focus of play outside the fiction. Of course they have to be the right riddles.