A recent article in a magazine sent by my Vet relates the problem of pets consuming items NOT designed for eating. While cats have this problem a little, it is major for dogs, especially big dogs. Here is a list of the most common objects that are swallowed by pets and that require surgery to remove:

balls (one dog had 5 tennis balls removed!)
bones
chew toys
corn cobs
hair ties or ribbons
panty hose
rocks
socks
sticks
underwear