#3 SURPLUS GUNS IN MAGAZINES: I recall as a cub scout seeing ads for switchblades in the back of Boys Life but that was about it. Later, I would see ads for old police trade-ins in Shotgun News in my early teens.
However, I heard stories (post WWII) there were tons of cheap 1911s (and ammo), Garandes, Bolt Action Springfields, Mausers and all kinds of other stuff for sale in the back of several magazines. I would love to have confirmation of this stuff.
Before the Gun Control Act of 1968, such ads were common because you could order a rifle in the mail. Here's a sample, do a Google search on "Klein's gun ads" for more:
http://upload.wikimedia.org/wikipedia/commons/9/9c/KleinsAd1963.jpg