Cough medicine
I don’t remember if my parents ever gave me cough medicine as a kid (they probably did) and it’s been a while since I was sick enough to need it, but let me tell you, I had no idea dextromethorphan was such a freakin’ miracle drug. I slept (if a bit restlessly) all through last night after a good dose of it, even though I have The Cough From Hell.
Wikipedia has some fairly interesting info on it.