Pocket Gun - Ruger LCP - Ridiculously small, but still reasonably powerful and usable.
Single Stack CC - Kahr CM9 - I think Kahr owns this form factor. Lightweight, thin, 9mm, decent trigger and ergonomics. Often imitated, yet to be duplicated.
Double Stack - Almost too many to mention here, but Glock and M&P get my vote. I like the simplicity of both designs and the weight advantage of polymer (for carry). Glock is the industry standard for reliability and durability imho, and also has a nice stock trigger. M&P has outstanding ergonomics. Both can be had for right at $500 otd, which is an incredible value.
All great guns. But the limit is $500 out the door, that puts both Glock and M&P out of the running usually. I also mentioned in the original post brand new. Looking for those affordable new outstanding handguns under $500 out the door as a standard.