It might change when I get my Colt Anaconda off lay-a-away...
...but for now I would have to say it is my S&W m66. It is one of the first run guns with the stainless sights. It is an amazing gun both looks wise and in the handling department.
It would have to be my factory D engraved 6" blue Colt Diamondback in 22. It probably isn't the most valuable gun, but it is the one that has the looks. It is not however my flagship shooter. Have no idea which one would get the nod there.