As Bob pointed out, a slipjoint is a non-locking folder with a backspring, just like Grandpa carried (probably the most familiar slipjoint to America is the Schrade Old Timer brand, even though they are discontinued.) They look good, perform very well, and have a pedigree and tradition you can be proud of. As I said, Case, with chrome vanadium (carbon steel, stains/rusts, but with good edge retention) and yellow Delrin (type of plastic) handles are some of the best bang for the buck. The Medium Stockman would be a good place to start.
I know it is illegal to carry a fixed blade in NC (I should, considering I live in Durham) but like I said, I have no idea about carrying in your car. A CRKT would work well for this purpose. Heck, even a thin Old Hickory or Henckels or Chicago Cutlery paring knife, in a milk-carton or cardboard slip, stuck in the visor or between the seats, would work pretty well.
Also, what are you cruising around in? A baseball bat and Buck 119 would be a lot less conspicuous in a Silverado than they would in a M3? Tailor defensive tools to fit the cars at hand.
As for getting a Benchmade- go for it. They and Spyderco make really good and really good looking knives. (I'm trying to think of a car anology- maybe BMW and Acura?) I like Benchmades better, because they have thumb studs.
One more thing- in Raleigh, Davi's Gun and Knife has excellent knife selection, including Benchmades and Spydercos. Not the best prices, but not the worst.
My goodness! I've never had this warm of a welcome at ANY forum, and I've been on quite a few. I think I will really like it here!
I'm a down to earth person and I'd only spend 200+ on a knife if A) I was feeling flush and slightly silly and B) I REALLY liked it, rather than it being something everyone has or says is good. That's a lot of money!
As for slip-joints, I've known and loved them - just never heard the technical term! I see why they're called that for how they "lock." I have two SAK's - a Cybertool 34, which I LOVE (fix a computer, pull out a splinter, write stuff, open a beer, snip tags, pop the safety off a lighter, and many other things.) I also have an Explorer from the mid ninties, and a Solo Alox, which is a really pretty single slip-joint that I'll have to find and take a picture of. They are good quality and low maintenance but I really like the single-hand opening function and neat design possibilities of lockblades. Not really a fan of lockbacks, but perhaps I'll widen my horizons and grow to like them!
I never knew that a fixed blade carrying knife was illegal here... learn something new every day!
As to what I drive, it's a Volkswagen Jetta with a few performance modifications done to it (suspension work, wheels and tired, chip and intake and exhaust, short shifter, motor mounts, etc.) I'm very active on NC's best VW club,
www.ncdubs.org. Great site for NC or just southeastern area Dubber's. I love my car so I am interested in defending it
as for Spyderco vs. Benchmade - I'm come to almost the exact same conclusion. Have handled and tried out a few of both, including my dad's Benchmade 610 Rukus. Love that knife but it's just too damn huge. It's an early production (numbered) model, I think. I love the spydercos but have never warmed up to the hole for a stud setup.
one last thing - I'm quite sure I have an Old Timer floating somewhere around the garage, from the paleolithic age! Will have to find it.
NINJA EDIT: I almost forgot - I'm quite familiar with Davi's, have fired on their ranges before and have drooled over all the handmade goods as well as the BM's and H&K's etc etc. I wanted and H&K, but got a S&W instead

Not quite the same.