It's been a while, and I do so take pleasure in these challenges, so I offer them here, in hopes that you'll enjoy them, too.
1. What happens twice in a week, once in a year, but never in a day?
2. Mary's father has 4 children; the first three are named 'Nana', 'Nene', and 'Nini'. What is the fourth child's name?
3. There is a word in which the first two letters signify a male, the first three a female, the first four a great man, and the whole word a great woman. What is it?
4. A man rides to town on Friday. He stays there for three days. Witnesses say he left town on Friday. How can this be?
5. How is a raven like a writing desk?
6. Who among you is the most disliked by the party?
1. The letter 'e'.
2. 'Mary', duh.
4. The horse is named 'Friday'.
5. They both open with a flap.
6. Not technically a riddle, as it has no 'correct' answer (I hope). Your group's reaction, however, may be quite amusing; it may even elicit some laughs as they reach a consensus. Afterward, just say "If you all agree, then it must be so" and carry on.
Not bad; quite entertaining, in my opinion. But those dealing with a particularly smart/intuitive/experienced player may need more. Something neigh unsolvable, perhaps?
These selections, while unquestionably intricate, are somewhat relatable, as they often deal with matters of chance, rather than pure, technical knowledge.
Downright nasty in complexity; feel free to conjure a solution of your own, as applicable in your setting of choice.