Og lays out his Firearms Wish List.
I've never really given mine any organized thought. As a collector, there are certain guns I would buy on reflex if I found them and I could afford them, but it's not like there's any real method to the madness.
There are a few that don't fit the pattern, however, that I still lust after. For example, at some point, I'm going to buy a Remington Model 8. And not a minty one, either, but an honest shooter, preferably in .35 Remington.
I'll own another Ruger No.1 RSI someday, too, but this one will be in 7x57mm instead of .243 Win. like the last one was.