This is not something which the queen carries with her every day, but she has been known to bring a camera on many occasions. Her Majesty has always been a keen photographer, and she apparently likes to snap pictures of world leaders for her personal collection.
According to royal author Phil Dampier, the queen has also been known to sometimes stash a number of other items in her bag: dog treats for her corgis, family photos, lucky charms given to her by her children (including miniature saddles, dogs, and horses), crosswords snipped from the newspaper, and a penknife!