This thread feels like it was made for me!
I am a collector, so there's a lot of stuff that I have that's rare and collectable. Let's see...
I have my old stash of Pokémon cards that I had when I was younger
There's my huge boxes of video game consoles that are older than I am, like a Farichild Channel F (1974!!)
My limited edition platinum Pokémon XD: Gale of Darkness Gamecube that I got at a thrift store for only five dollars (not even kidding)
My old prints of TokyoPop manga like Lupin III
An original VHS copy of Star Wars: Episode IV (it even came in a faux leather tape case!)
My literal mountains of other VHS tapes cluttering my closet
My extensive library of Stephen King novels (haven't touched it in a while, though)
Of course, there's also my growing collection of Transformers figures (I can't get enough of the stuff, as you can tell by my avatar)
And tons more. I'd list the rest, but I'd take up the entire thread before I was done, so I'll leave it there.