A while back, I tried to answer a question; if I could pick any, what guns would I buy? And I came to the conclusion very damn few, and some only with certain conditions.
I would love to have a Sharps in either the .45-110-550 cartridge, or .45-70, but only if I had access to a place with a range going out to 500 yards or so. I'd really like to try shooting one, but with a rifle like that you need long ranges for regular use; shooting it only at 100 yards would not be allowing it to show what it can do.
One of the British Martini-Henry rifles, in .577/450 of course, would be interesting. The history behind these by itself would make it worth having one to look at and handle. Just store it right next to your copy of 'Zulu'.
A Russian Nagant revolver? Possibly, just because it has one of the two oddest revolver actions ever made.
At the 45th Infantry Division Museum, in the parking lot, are a pair of 37mm anti-tank guns. Now if you had one of those in working condition, and a long distance to shoot it in, and the stuff to make solid shot to shoot... BIG bang!
I can't remember offhand who makes it, but a company makes three scale models- working- of machine guns. The 1917 Browning water-cooled, the 1919A4 Browning air-cooled, and the M2 HB Browning .50 caliber. All exactly scaled down, tripods and all, and semi-auto. AND, they fire either .22lr or .17 Hornady. Any of those would be seriously cool, and a fine centerpiece on the coffee table. (side issue, is it still a coffee table if you don't drink coffee?)
A S&W Model 57 .41 Magnum, just because I've always liked that cartridge.
Maybe a 1903A3 Springfield.
Lots of stuff I'd like to try out, like the .500 S&W, but not many I'd really want to own. I'll have to think about this a bit more.