I love these threads and understandably they are mostly comments made to toddlers/preschoolers, but if you think it gets better as they get older think again!
My dd is 18 and I'm still having to say stupid shit! 
"Because if you leave food out the fridge it goes off! Yes even if 'it's only been a couple of hours'"
"I am not made of money"
"It is after midnight turn the damn music off"
"No I'm not sniffing it to see if it's clean enough to wear despite living on your bedroom floor for a week"
"Well of course it's hot it's been in a hot oven!" She seems to think oven gloves are for wusses!
"No it's not cancer/the plague its just a zit/rash/whatever"
"No you are not permanently deformed just because squeezed the zit"
"No you do not look ugly just because your hair won't go EXACTLY how you want it to"
(Last 3 seem to occur in week before period)
Don't even get me started on conversations started when she's pissed which can span from the ridiculous to the very moving and revealing.