I drive an XJ so I'm not sure how well this works for everyone else, but I just squeeze my 2D Mag in between my drivers seat and the center console:
This works way better than putting it between the seat mounting brackets on the left side and its also totally free.
Escape Hammer Mount:
I know this is totally overkill, but I got the gadget for Christmas and I figured why not? It came with a mounting bracket, but that was bulky and required drilling holes in my console:
I just used three Velcro circles I had lying around. Its easy to reach here, even if I manage to roll over It's also a small (ineffective) flashlight and a seatbelt cutter.
Trunk Milk Crate:
I had the bungee on the floor of my car, and I found the crate at the bottom of a local lake I just ran the bungee through the side of the crate and hooked either end on to the metal luggage ties on the floor.
This works great for groceries, or any other random stuff that's rolling around like my copious coolant bottles (thats another thread), and it's easily removed.