First Aid Kit: A First Aid Kit of some sort just in case you or your buddy gets hurt. Know what is inside your kit and know how to use it. A kit that is in a water proof container works the best for kayak fishing.
Kayak Pump: This is one thing you hope you will never need but if and when you need it, you will have it. It's just like a PFD.
Personal Floatation Device (PFD's): This is required by the USCG to have on a kayak. There are PFD's that are made for paddlers and kayak fishermen. The best ones have places to attach things like a whistle, VHF radio, and a knife. Remember you need to wear your PFD. If you have it in your hatch you may not have time to get to it when you need it.
Knife: This can help you if for some reason you need to cut something. Keep it close just in case you need to use it fast. I like a small diver's knife because it won't rust.
Flag Not Included, shown with optional Silent Snaps.