Tis far better to have a kit, and not have a flat, than to have a flat, and not have a kit...

My emergency bag has two tubes and a patch kit. I usually just change tubes, and leave patching for when I get back home. Allen keys, multitool, pressure gauge, and spoke wrench round out my kit. I've needed the spoke wrench twice now, for broke spokes (I've now pointed that fairy at you!), to get me back home without brake pad rubbing.