LCP Ruger, 380 or a S&W 442 (blued) or 642 (stainless) make two good pocket guns with the proper pocket and proper holster (Robert Mika makes an exceptional pocket holster that is all function, no frills and very reasonable in price)! I am going on my third year with my two RM Holsters I purchased and use nearly daily! They are excellent at keeping lint, dirt, perspiration, etc. off the gun and, most importantly, keep the trigger guard covered at all times for safety!
For safety-sake, I never put anything else in the pocket my gun is in. A key-ring could easily snag the trigger and in an emergency, one might be anxious to yank the keys out to get to the gun thus inadvertently pulling the trigger!
Also, for extremely large pockets, I have a little trick -- putting the holster with gun, snug up to the inner edge of the pocket and then drawing a line with a marker to indicate where to sew a partition (divider) line up the pocket so the large pocket makes the pocket holster fit perfectly without the holster moving around every which way!
For small pockets, I need not do this sewing at all.
My wife showed me how to use her sewing machine and, with the pants off and gun holstered in the pocket, I just mark the 'dividing' line a bit wider than the holster, then lay the pocket out flat onto the sewing machine and go straight back-and-forth four or five times (without the gun and holster, of course). When this results in a real small (useless) partition within the pocket because of the new divider, I just arch the straight-sewed line up-over to the nearest upper corner so lint, debris, etc doesn't get stuck in the narrow partition!
On several pairs of pants with exceptionally large pockets, that extra space on the other side of the divider is large enough to put a couple of .38 SpeedLoaders in or an extra magazine for my LCP. In fact, sometimes, I use that wider space to slip my cell phone in! Since the pocket is divided, anything put into the smaller pocket, adjacent to the gun with holster, does not interfere in any way with the gun, the holster and even drawing the gun!