Only gun I've ever sold was a duplicate; I had two of something, and I kept the one in better condition.

From your list, I would sell the Shield, even though it's your functional choice. Why... because you can replace it cheaply with another right now. Why not... because unless the buyer doesn't do his research, you shouldn't get much for it.

I wouldn't sell: anything that approaches "icon" standards, especially if it's not in production anymore.

Seriously- if you just have to sell, sell a new polymer gun that has no sentimental attachment, and that you can easily and cheaply replace.