If limited to military surplus, and to the average hunter or farmer, the answer would have to be that the main arms were Krags and .45-70 trapdoors (.50-70 ammunition was nearly unavailable, even then). NRA members (some 20,000 or so) could buy M1903 Springfields, but they were not on the market. Most of the others, like rolling blocks, Lee-Navies, Spanish Mausers, German M1888's, etc., were uncommon and scarce.
The other common firearms were double barrel shotguns, mainly those we now consider old junk - Damascus barrel, no-name guns that did the job of providing meat for a family. Only the well-to-do owned Parkers, Foxes, or the better grades of Ithaca, and guns like the Winchester Model 12. There were .22 rifles, almost always a single shot or a pump gun (bolt actions were still uncommon, lever actions unusual).
Center fire rifles were almost always Winchester lever actions, with a smattering of Remington pumps and autoloaders. The famed Winchester Model 70 was expensive and owned only by people who were both well-off and oriented toward quality guns.
And there were handguns. Again, the most common were the least expensive, the IJ's, H&R's and H&A's sometimes scorned today. Colts and S&W revolvers were costly and uncommon. Automatic pistols were considered "Army guns" and far too exotic (and expensive) for the average person.
Of course there were dozens of other guns, and "gun nuts" might own hundreds of unusual types, but those were the most common and the most likely to be found in the home of an average hunter or farm family.
Jim