These are partly ones I've seen myself, and also ones from this book I have. XD But they are all stupid.
Personal Experience:
* Washable dog blanket. Caution! Remove dog first. (on a dog blanket)
* Contains nuts. (on a jar of mixed nuts)
* If you are unable to read this sign, go and find one of our staff. (sign at the library; you'd think they'd know better. XD)
* Open bag. Eat pretzels. (on a bag of aeroplane pretzels.)
From the book:
* Do not eat toner. (on a laser printer cartridge)
* Do not use in shower. (on a hair dryer)
* Do not attempt to swallow. (on a mattress. Lol wut?)
* Do not use orally. (on a toilet cleaning brush... ew, I should hope no-one would! O_o)