I had a small flashlight and a pen sized screwdriver in one of the outer side pockets, and the TSA people even thought I was carrying tools prior to them xraying it. Holds my speed graphic, light meter, an extra lens, and a bunch of film holders. If I go out with a few less film holders, I have room for gatorade too.
However, if you were looking for a bag to leave unlocked in a car, thieves will take tools far quicker than old camera equipment. In such case, other's advice about a cooler might be better for car storage.