I was going to title this thread "Your oldest possessions" but that might be confusing because I'm not referring to the age of the items (e.g., antiques or heirlooms) but the amount of your life you have owned them.
I have a stuffed elephant named Fenwick that my father gave me when I was too young to form memories of receiving it -- probably before age 1. I do remember how he lost one of his eyes 6 or 7 years later though.
I also have a sleeping bag that was purchased for a Girl Scout camping trip when I was 9. It's green outside and the flannel lining was cream-colored flannel with pictures of deer. However a couple days before the camping trip we had it spread out on my bed and our cat decided that was a good place to go into labor, so it had to be laundered and the nice cream-colored lining became dingy green before I ever slept in it.
These days I'm more likely now to use it as a padding to sit on, like a blanket or cushion. It would be a tight fit to get inside. But I had been keeping it in my car trunk in case of cold-weather emergencies.
I used to have a plain green sweatshirt that I bought in 8th grade and continued to wear well into adulthood. Eventually it got too tight and there was a rip between the sleeve and the wrist cuff, so I got rid of it at some point, but it amused me in my 30s to be wearing something I'd had since I was barely a teenager.