What are the common subjects asked for riddles?

Answer:
Riddles can be of a wide variety of subjects. But remember, even if one knows the answer to a riddle it's not for them. All riddles are expressly meant for the Batman.

-Edward Nigma
First answer by Trolltool. Last edit by Trolltool. Contributor trust: 0 [recommend contributor recommended]. Question popularity: 0 [recommend question].