Most of the ones I've played with so far were the short-bladed kind, which are not only non-threatening looking but also legal in the widest variety of places.
If you're not constrained by regulations regarding blade length or a locking blade on your folder, there's also the "stylus" type of gents folder, which I hadn't really played with before, so I decided to give the CEO model from Columbia Knife & Tool a whirl. (I sold some old ammo at this weekend's otherwise dismal Indy 1500 gun show and decided to share some of my small windfall with Brad, the knife guy.)
As the name would suggest, this style of knife is very slender, and will generally slip into any pen pocket large enough to accommodate a fine writing instrument, like that Monteverde Regatta.
You could carry it in your pants pocket, I guess, but I think its natural home would be a shirt or jacket pocket where pens are normally carried.
The blade is a bit over 3" long (3.11", to be technical) which can run afoul of local regs in places like Boston or Chicago. It's made of 8Cr13MoV steel, which is a lower-tier Chinese stainless that's roughly similar in properties to Japanese AUS-8... you're not getting exotic alloys at this price point. It's less rust resistant than good ol' 440C but easier to sharpen and less likely to chip in my experience.
There are complaints from reviewers at Amazon about the lack of a flipper on this variation (they make one with a flipper for a couple bucks more) but I prefer the slimmer profile of the flipperless one. This isn't a tactical knife.
The pivot is smooth and fitted with a ball bearing; a good shove on the thumb stud will often pivot it right into the locked position, although this is not an assisted opener. The pocket clip makes it sit nice and low and only someone who's paying a great deal of attention to your chestal region will notice it's not a pen. The lock is positive and the blade on my example was nice and sharp right out of the box. It's well up to normal everyday knifely chores.
Given its intended use, I give it a solid B grade. It's nothing exotic, but it's good-looking in a very clean and simple way, and the price is right.
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