Seldom. Let´s see what´s in my 1 bedroom apartment, for Japanese media alone.
My Behelit pendant, a few posters and my tattoo. This should be it but i will get Berserk Musou next month and i have 5 Japanese consoles around my feet and desk.

I ain´t a bit fan of keeping anything frankly. I am even (nearly) all digital with my comics.

I am not merchandise type of guy... I don't have collectible merchandise of any kind really...

That's actually a good debatable topic. I mean merchandising is to help fund the production of the anime/manga, right? But what percentage actually gets there, and how much does it really affect whether we get that follow up season? I mean really, when I bought a Kakashi (from Naruto) chibi keychain from a big anime merch retailer in our country, I thought to myself, does this help the budgeting issues of producing new episodes, how much money is forwarded to them , and is this even licensed and are those royalties given at all to the proper owners? I mean copyright is a big issue in some countries and a lot of unofficial merchandise are up for grabs. Etc etc.

Plus there's always the anime that's essentially there to sell toys. That didn't stop me from getting any sweet sweet zoids though, or yugioh cards, crush gear, beyblades, gundam, and the like.

Edit: Ran my mouth without thinking for a second there. Yeah, @Sakura_Hikizaki is probably completely right.

I have a plushie and some key chains.

Keychain, some posters, but I'm not that much into buying merchandise or at least I haven't seen something I really want to buy yet.

I do have a good amount of doujinshi though

Voted for never but then I remembered all the Pokemon trading cards I've bought when they first came out... So it turns out I did spend quite a bit.

It's mostly figurines that I get these days, but I did go through a keychain/poster phase at one point.

Bought a few more DVD/blu-ray's recently when the sales were too good to ignore as well.

I have a few plushies but they're mostly from the Pokemon Centre when I was in Japan and I went a bit crazy getting anything that caught my eye. I don't know when I'll be able to visit again after all! I spent around 10,000 Yen in the Pokemon Centre that day haha. Worth.

I used to buy manga almost exclusively, but then I fell into the figure-buying world a few years ago and now I can't dig myself out. So, yeah, "some". (I also buy CDs regularly, if that counts? Though I'm much more focused on specific artists in that case, instead of what anime it's from.)

I have a few keychains/clear files of things, but that's mainly for series I really, really like. (Mostly Kino no Tabi stuff, now that I think about it.)

Oh, right, and I also enjoy buying artbooks a lot, but I mostly focus on specific mangaka in that case. (I have artbooks from Toume Kei, Fujiwara Cocoa, toi8, and Tiv just to name a few.) I think the only series specific artbook I have is Kinako's Gatchaman Crowds artbook.

Some: Before 2013 I only collected manga volumes and related art/data books, Yu-Gi-Oh! trading cards and a few anime DVDs/BDs. This changed when I first visited a convention near Munich in 2013. After getting talked into buying a figurine, I started collecting them. Right now I own 26 figurines and have pre-ordered the 27th one. Some posters, a paper fan and smaller stuff like a key chain, pins or a wrist band found their way into my collection, too. After abandoning anime DVDs/BDs and YGO! I started getting into the Weiß / Schwarz TCG (because I play the KanColle browser game) which is a grave danger to my wallet. But my main interest still lies with collecting manga volumes (getting closer to 1300 volumes).

I am supposed to get these cute little kodama from Mononoke Hime but I ordered them months ago and haven seen anything.

I've awlays wanted to get a Weiis Schwarz deck (Monogatari series probabaly), but I'm scared I'll get sucked into another card game and waste more money than already do on them.

I'm a sucker for sculptures, but that will have to wait till I move out of my parents place. I have quite a few prints that are stuck in my closet for the same reason. Almost forgot my custom playmat that I made from a painting of Maya Nastume by OH! great.

So a few things, definitley want more.

I used to buy keychains, and I would like to buy figurines, but given their prices, I'm too poor to do that. Haha. I already spent way too much buying digital manga.