For me it’s driving while under the influence. If you couldn’t tell, I like me some ganja. However I have long since held the belief that it is utterly insane to drive while under the influence of most substances, with maybe nicotine and caffeine being the exception. All too often I see other stoners smoking and driving, which I simply can’t fathom. I’ve only operated a vehicle once under the influence and it was just to move a U-Haul around the block to a different parking spot, which was such a scary experience while high that I refuse to even consider getting behind the wheel again while high.
I had a friend running a campaign where a big part of the local kingdom was that it had a constant, annoying bureaucracy. At one point we were set to meet the king, and the party all had to wear ceremonial scarves. As part of the bureaucratic obstacles the DM had it that we’d been given the wrong color of scarves, and therefore the guards weren’t letting us pass.
I instinctively just did the Lionel Hutz “I’m not wearing a tie at all” bit with the scarf. The DM was so speechless that he said the guard was speechless and let us pass out of confusion.