For me it would have to be the following three. All prewar naturally

Holland Royal .600NE (Rewa rifle)
Purdey .600NE SLE
Jeffery .600NE snap action

Honorable mention- Hartmann & Weiss 600NE (royal clone) the only .600NE double they have made.

The .600NE is the ultimate double rifle caliber. If you have ever fired one you will know what I mean.

Bike Rider