Baseball cards until I was caught stealing from my favorite baseball card shop (remember when that was a thing!) and then was too embarrassed to ever go back.
Regular books, preferably all with the same edition and cover art
OK Cola cans.
VHS then DVDs then Blurays
Magic The Gathering Cards
Various suits of armor and matched weapons within World of Warcraft.
I'm not touching Pokemon Go. I'm terrified of Pokemon Go. If I get anywhere near Pokemon Go I know I'm not capable of stopping. I'm not sure I'm even capable of slowing down. Ten years ago I spent literally 8 hours a day playing video games and collecting suits of armor and grinding out levels and armor and reagents and stuff.
Pokemon Go is a dagger aimed directly at my ability to be an adult, a Sword of Damocles designed to sever me from my hard-won ability to function as a 37 year old man and if I try to catch them all--hell, if I try to catch even one--I'm gone. It will all be for naught and I'll be hip deep in [common Pokemon characters] and searching for my next [rare Pokemon character] fix.
I can't even research a proper Pokemon joke to fill in the blank for fear it might tip me over.
I salute all of you out on the streets leveling up your characters or fighting for gyms. I'm not saying it's not for me. I'm saying it is for me, and I need to stay away lest I lose this version of me which I love only go become what I once was.