I like the KelTec P3AT. It's the most size-efficient gun I know, small/light/flat and reasonably powerful. Mine is very reliable. I dumped my previous pocket gun, a J-frame S&W revolver, once I got the KelTec.
I can carry a Glock 26 in the front pocket of my cargo pants, but it's a lot of gun, and I'd just as soon carry it on the belt.
I have thought about getting a small 9mm for the pocket, like a Kahr PM9 or a KelTec PF9, but I'll only do that if I go to full-time (rather than occasional) pocket carry. I still have concerns about the PF9's reliability.