I can't help but think of ammonium tri-iodide, a contact explosive that was common in my college (practical jokes) - but I lived with a bunch of budding organic chemists. According to them, making it (and using it in a practical joke) was something of a rite of passage.

More on-topic, there are 'grades' of Christmas crackers. The good ones have things that an adult might want (e.g. keyring eyeglass screwdriver).