At one point I was trying to get all of the major interwar "art deco" pocket pistols. There is such a great design diversity to collect with these little guns, everything from the Colt Pocket Hammerless to the Savage and H&R automatics to the PP and '14 Mausers.
I almost forgot, I collected WaA marked German WWII pistols for a while and had a few .32 ACPs. Eventually sold all .32 ACPs and only kept one VOPO Luger that is an outstanding shooter.