From my last Jeep:
Night vision goggles
SW M&P 9mm
500rnds 9mm (Remmington Golden Sabre)
Mossberg 590A1 (foldable due to available space in vehicle)
200rnds 12ga. slug and buck (each)
2 units of Semtex (and related 'wiring')
Quarter panel pod-mouted GD M134 (6 barrel 'minigun') w/350k rnds 7.62x51mm (hench the foldable stock on the Mossberg)
Home-made hood-mounted flamethrower with 2 5gal fuel tanks (who needs a front passenger seat??)
...and this bad boy:
A fire extinguisher seemed counter-productive so I didn't carry any of that nonsense.
No 2-way radio, no cell phone.
I didn't need help or backup...
I WAS BACKUP!!!
Then I met a friend, that grew into a few more. I suddenly realized that I was insecure and didn't need so much stuff....so I got rid the Gerber Multi-Tool