tie down straps, scissor jack, pin for the trailer hitch, tire pressure gauge, rags, sockets for the wheel nuts and jack, flashlight and love.
I keep love in seat-back pocket. easier to reach that way.
You have to make sure you don't leave it in the same place for very long, or you'll end up with a GhostRing on your seat back.
And back on topic, my storage bin has a 10" woofer in a custom enclosure.