The Estwing 26" axe now on sale online at Home Depot would be a fine addition to one's vehicle tools/armaments, at a fraction of the price for combat axes and knives.
It's about 6" too too long and a tad heavy (3.5 lbs) for a combat axe (requiring more time to "re-cock," during which time your enemy can attack), and it has a flat head (for hammering in tent pegs and such) rather than the point (or pommel) most combat axes have (see image in upper right sidebar or this larger one). But it has good balance and it's heavy enough to do major damage should the occasion arise (by either cutting a deep slice to the shoulder, side, or leg; or cracking the skull with the flat side).
In combination with a handgun and an assertive style and expression, it would make one look fearsome, scaring off minor hoodlums looking for more passive victims. And, it's legal to carry in one's vehicle in all states, counties, and cities (AFAIK).
It's light enough and short enough to carry on all but the most strenuous hiking trips, and will do some serious wood chomping.
Estwing also offers a 16" axe (which is a hatchet).
If interested, see also this 24 NOV 2004 A-C-E article on battle tomahawks.
I've come close to buying one several times in the store I visit, but they're now sold out.
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