In that category I own a SIG P290RS, Kel Tec Pf-9 and a Ruger LCP, and I used to own an NAA Guardian .32ACP. I have shot a Kahr PM9 and MK9 extensively (they were owned by one of my closest friends), I rented a Kel Tec P-11 many times, and I've shot a Kel Tec P-32 on a few occasions.
I love my SIG P290. It is heavier than many of the other guns in this category, but that contributes to its feeling and shooting like many guns significantly larger. I can comfortably shoot this gun all afternoon, and it is easy to shoot it accurately. Mine has been reliable, and I do trust my life to it. It is a bit heavy for pocket use, but with the right pants and right holster it is doable, and I love it IWB. The Kahr MK9 is a little smaller but heavier, but I went with the less expensive P290 when buying for myself.
For a true pocket gun, usable in most pockets, I'd go with the Kahr PM9 if money was no object, but they've become expensive and for most of us, money matters. I liked the trigger of my Kel Tec Pf-9 better than the CM9 I tried while shopping that category, and I went that way. The Pf-9 is reasonably accurate, and after some break-in issues, it has been reliable. However, it is no fun to shoot (I put it up there with steel framed .357mag small framed snubs for how painful/unpleasant to shoot it is). It is also a tad big compared to some of the competition, though at under 13oz it makes a great pocket gun. If I was to do it over, I'd probably get the Kel-tec P-11, Kahr CM9 or Ruger LC9, and I'd strongly consider the Taurus 709, but for now I'm keeping the Pf-9 (and may until/unless I'm ready to buy a PM9).
As for the LCP, it is reliable, but the sights are tough to use. I wish I bought it with a laser sight. That said, I think some of the small 9mms work as pocket guns well enough that I can't really think of many circumstances where they wouldn't work yet I could carry the LCP. I will probably sell it, but I haven't been able to bring myself to do so yet (once you have something that small, it is hard to give it up). My suggestion would be to buy one of the small 9mms first, and only if you find they are too big to go to the small .380s.
I never really liked my NAA Guardian. My biggest issue was that I could never trust the caliber. In fact, if anyone near Baltimore has a .32ACP, I may have a few boxes of ammo left that I'd love to trade on .38spl or 9mm. If I did want a small .32, I'd probably go with the Kel Tec P-32, I actually enjoyed that gun and may someday buy one just for fun. The P-32 is smaller than most .22lr and .25ACP pistols, very few guns are lighter or smaller.
So, bottom line, if money is no object I think the Kahr PM9 is the best choice in small pocket/pocketable guns, with the SIG P290RS taking a close second choice and first choice for those of us on a budget.