I collect NES and SNES games. I bought most of my NES cartridges back in or around the year 2000 when they were dirt cheap. Most of them were under fifteen dollars and could be procured at Gamestop/Funcoland stores. I'd walk in, see a massive wall of all the best games and just go on a shopping spree. I think I have about seventy games now and don't think I want anymore. I'm not a completionist and only care about having the best of the best.
My SNES collection is still a process since, unlike my NES collection, I had to start collecting a few years ago and their prices now are way too expensive to get all at once. I'll probably be collecting until I'm old and grey unless I win the lottery or, sell some of my novels... which I'm waiting on right now.
My favorite is my complete collection of Megaman cartridges 1-6. Got them for five dollars a piece and had no idea they'd ever increase in value like they have. I keep those babies on a shelf.