“ Adventurers are to capture an unknown monster for examination (for a sage or wizard) but they are themselves captured by the monsters, and researched.”
“ An evil ruler got the idea of mixing a trampoline and a gallows together. As long as the one to be hanged bounces on the rubber trapdoor it won't open, but bouncing gets very tiring after a while.”
“ War of the Roses as a campaign plot. Two noble lines converge somehow, each line thinks it has the rightful claim to the throne. Deciding this long ago was handled by some divine intervention, requiring both houses to come together at some point. They aren't so willing to get together this time. Civil war, or a new king?”