The most recent one I've seen floating around is: disgruntled person asks LLM how to wipe out humanity; said LLM cheerfully explains how to design a custom array of highly-contagious, slow-onset, high-fatality viruses; LLM then helpfully orders them from an LLM-operated lab and provides effective instructions on how to spread them; disgruntled person follows the instructions, and more or less everybody dies.