Make a whole bowl of cookie/cake dough and eat it raw
Do you remember how as a kid (and even now) the best of making cookies or baking a cake was always when you could eat the rest of the raw dough from the bowl? As a kid I always thought that once I was old enough to do whatever I wanted I would just make a whole bowl of dough and just eat it.
Why do I never do that? It wouldn't even be expensive and I'd probably feel so sick afterwards that I'd be cured of that insane wish.
Ah, and don't tell me about salmonellae. Been there, had them, survived. So that trick doesn't do it for me.