I use to collect Indian artifacts, all found by me. I had around 300 good peices but lost every one of them in a house fire. It was beer cans when I was younger, sold all those to. I also had the RC pop cans with the ball players on them back in the day, My younges son is now collecting the same RC cans when we find them.
Arrowheads and other old relics I can find, old glass bottles etc. I have shadow boxes all over my house full of this stuff. Also old and custom knives, antlers and most importantly..... big deer heads.
I used to collect baseball cards. Still have several thousand of them but haven't bought any in close to 20 years.
Trail cameras... I used to collect rocks/gems, as well as baseball cards back in the 80's and 90's. All of which are pretty much worthless nowadays.
Historical Newspapers - 11/11/1918, 12/7/1941, VE Day, VJ Day, 6/25/1950, Kennedy Assassination, Apollo Moon Landing, 9/11/2001, plus others. Collect them as they show the what happened and the American Reaction to those times.
Basketball, football and baseball cards when I was younger. Ertl 1:64 farm machinery, animals and sheds from when I was born and still do now. Golf balls from every state and country I have been to.