Oh Noes! Dihydrogen Monoxide!
My physics teacher used to threaten to spray it at us if we incorrectly answered a question. One of the previous years to my class, a concerned parent called up the principal and left a complaint citing how dangerous the chemical compound could be, even though they never heard of it.
Hell, I used to threaten people with it in college, many people (who supposedly passed chem) would just step back in horror and confusion.
Fantastic site Gene :devil: