"Caution- Coffee is hot!"
"Warning- Using hair dryer while in the shower may cause electrocution!"
"Be careful- Superman costume does not enable you to fly!"
I've come across some things that I didn't see any warnings for that startled the hell out of me.
When drinking green Gatorade (at least after throwing up all day and not really having anything else in your system), there's a chance your pee will turn green. (Thank you Gatorade for inspiring this post about fifteen minutes ago.)
In some states, it is very easy to accidentally end up common law married. (Congrats to you-know-who. Sorry I didn't send a present.)
And finally, should your store be next to a photography studio that often has laughing children, there's a very high chance your staff will hear laughing children with no children in sight...and they will be convinced the store is haunted. (In a year, I've had about ten girls approach me about it. To be honest, I might make my own warning sign because I'm tired of repeating myself.)
I'm not even gonna apologize for this. Blame Gatorade and the green pee.