To me the best 9mm pocket pistol choice right now is the Kahr CM9. It is carryable in most front pockets and is definitely smaller and/or lighter than the LC9, PF9 or the others mentioned above. Yet it is still nice to shoot, accurate, comfortable, with a nice trigger.
I am not a Kahr fan these days, they have all been finicky or worse as far as I'm concerned. But so many like the CM9 and claim it's 100% reliable that maybe it's just me.
And mine wasn't bad--8 malfs in maybe 1200 rounds, and all were either longer rounds or were fired in the weak hand. But I would rather not think at all about my defense guns, what load I have in them or how I'm holding them, or how clean or well-lubed they are....revolvers look better these days to me....that and the LCP.