Well I am not familiar with elite custom gunmakers and I'm not sure I would want an ultra expensive firearm because then I would be too afraid of damage or loss to actually use it!
Sorry for harshing the collective fantasy. ;-)
Upland birds is the type of hunting I do most so I would have to say that a very fine quality 12 guage O/U make me real happy!
As for rifles, the Ruger Model 1 International in 7mm magnum would be perfect. (They don't seem to offer the 7mm Mag with the international style stock, so that would be the wish fulfilment part!). My Mannlicher-Schoenaur has that kind of stock and I really like it!
Pistols - I'm a wheel-gunner at heart and .357 mag is my preferred caliber. I'd love to have a blued S&W 4" L-frame "B-B-Q gun" with real elephant ivory grips and a bit of fancy leather to carry it in. Yeah, that would be cool!