I bought a 3/8" thick cutting board from Amazon and made my own 'extra' dividers.
I keep a fire extinguisher on the driver's side and didn't want it rolling into the main section.
Items I keep in both of our vehicles:
Extendable lug nut wrench (OEM wrench is just too short)
Fire Extinguisher
Amber LED magnetic emergency strobe light.
Small first aid kit
Blanket (doubles as protection for the rear cargo carpet)
Extendable shovel (winter only here in MN).
Towels (winter to dry off if it's snowing, summer in case bathing suit is wet after boating)
Flashlight (the little Ryobi with the USB rechargeable battery works great)
Explorer only:
Hitch & towing accessories.
My wife gives me shit, but hey, I'm always prepared!
(I'm ex-Military Police, hence the 95B in my user name - old designation for MP)