I don't think I have much "official" merch that's rare or anything. I have a Famicom micro and the Dialga/Palkia DS Lite, and a random Phantom Hourglass cel that keeps popping up every time I clean my room. But for fun, I'll list off what game-related things I have lying around my room.
*Those Club Nintendo Zelda posters (I have the Twilight Princess one hung up because the others don't really match my room :V)
*Some headphones I got with Super Scribblenauts. Purple with polka-dots! I find myself using them as earmuffs more than I do headphone covers.
*Two Zelda shirts
*One Homestuck -- ok, that's a comic, not a game, but I'm counting it because it's nerdy -- shirt. Yay Jade!

*An Animal Crossing doll and a Luke (from Professor Layton) doll
*The official Mother 2 guide
And out of my fanmade things....
*Ness (who's wearing a Fangamer pin lolol), Ana, Paula, Kumatora, Mr. Saturn, Rope Snake, Lucas, Claus and a Fobby are currently chilling in my room right now.

Collection is growing because I can't stop sewing.
*Sky Runner poster from Fangamer
*A couple random doodles of Mother characters on my corkboard
*A little Lucas keychain that I made out of boredom, but it came out pretty bleh.

*A Franklin Badge that I wear pretty much everywhere. (If I had an official one I still wouldn't wear it. Wouldn't risk losing that thing!)
I have a lot of Pokemon things too but I like to pretend that they don't exist