Futility Closet published an old riddle (dating back to the late 1700s) that has remained unsolved to this day.  We suggest that the answer might be hiding in plain sight.  Here's the riddle:

In the morn when I rise, / I open my eyes, / Tho’ I ne’er sleep a wink all night;
If I wake e’er so soon, / I still lie till noon, / And pay no regard to the light.

I have loss, I have gain, / I have pleasure, and pain; / And am punished with many a stripe;
To diminish my woe, / I burn friend and foe, / And my evenings I end with a pipe.

I travel abroad. / And ne’er miss my road, / Unless I am met by a stranger;
If you come in my way, / Which you very well may, / You will always be subject to danger.

I am chaste, I am young, / I am lusty, and strong, / And my habits oft change in a day;
To court I ne’er go, / Am no lady nor beau, / Yet as frail and fantastic as they.

I live a short time, / I die in my prime, / Lamented by all who possess me;
If I add any more, / To what’s said before / I’m afraid you will easily guess me.

Here's our answer, in black text on a black background.  Highlight to view:  A flame "rises" as it is lit, though it doesn't sleep because it is not technically alive.  The eye is a reference to the eye-shaped blue part of the flame, at the wick, that burns the coolest.  It gives pleasure and pain (romantic candlelight and burns to the skin of both friend and foe).  It's punished with many a stripe (uniformed firemen beating down the flames).  It ends its evenings with a pipe (lighting the tobacco, of course).  It never misses its road (the pathway it travels as it consumes fuel) unless met by a stranger (water is a stranger to fire).  It never goes to court because it isn't a person, though it is as refined and dazzling as royalty.  It is lamented by those who possess (hold) it, for it burns.  Its habits change often in a day, as candles, ovens, and hearths are lit for different occasions.  It lives a short time (not really such a thing as an eternal flame).  It has losses and gains — the yields of lost wax.

"The Riddle of the Sphinx": an illustration from The Gate Beautiful by John Ward Stimson (1903).

Here's a game of "What am I?"

Your clues:

• I am an arrogant slap in the face from across the room.
• I am an ethereal corset trapping everyone in the same unnatural shape.
• I am a lazy and inelegant concession to fashionable ego.
• I am too often a substitute for true allure and style.
• I am an opaque shell concealing everything—revealing nothing.
• I am a childish masque hiding the timid and unimaginative.

What am I?

Answer: Perfume (The answer is in black text on the black background. Highlight it to view.)

These clues are courtesy of Christopher Brosius.