OEM tool kit, tire plug kit with air supply, first aid kit, sunglasses, and bring my cell phone and a credit card. Anything else is trip or weather related. Long winter backroad rides are a lot different for cargo than short summer Interstate rides. About 90% of the time I also carry a camera, and part of the time a gun. And during the winter my Gerbing clothes and rain gear never leave the bike.
You asked about parts - if ya can't fix it with duct tape, bungee cords, and tywraps, you are broke down.