Well, since handguns come in calibers, my first decision has to be to choose the perfect caliber. For me, that is the .41 Rem. Mag. From there things get a little muddled.
The first .41 almost 20 years ago was a Ruger Blackhawk with 6 1/2" barrel. It was used and somewhat abused when I bought it, but has the nicest single action trigger I'd encountered, until the Freedom Arms gun came along a few years ago (also in .41). The truth is all my .41s are ideal for one thing or another. Depends on the task at hand.
Punching targets is ideal for the 8 3/8" M657.
The M657 Mountain Gun is the ideal holster gun.
The M357 is the ideal back or day pack gun.
The M58 is the ideal combat revolver.
The 3" M657 is the ideal BBQ gun.
The 4 5/8" Blackhawk is the perfect casual plinker.
The 7 1/2" Freedom Arms is the perfect gun to load hot and heavy for hunting and long range shooting.
There are a few Marlin 1894s in .41 mag. around here too, but they don't count in this discussion.