Dead Or Alive: Dimensions, 3DS – £8
Dead Or Alive: Dimensions, 3DS – £8 delivered
or £6 if you collect in store.
I’ve heard a few rumblings that this is the game you’ll need to be able to use the upcoming homebrew channel that is being developed, which would make sense because it has an in game photo mode that would potentially result in a vulnerability.
I’m listing this now since the price will probably go up later on if/when it is confirmed that this is the game required for the hack.
GAME also have it for £8.99, and as long as you don’t break their seal, you’d be able to return it for a full refund (I’m unsure what CEX’s policies are in this area).
Update: via Delusibeta, CEX have a similar returns policy to GAME, although it’s 14 days instead of 28.

Check @smealum twitter for updates, btw he said not to buy doa (yet)
I have also heard Steel Diver and Super Street Fighter IV mentioned…
Buying this for the homebrew channel is a shot in the dark. However, the channel creator has mentioned the game in question is old and cheap, and that it’s not widely available on the eShop. There are a few theories out there but I wouldn’t jump right in.
DOA Dimensions is a good game though, so there’s that.
Well buying it and keeping it sealed so you can return it is like a shot in the dark except you get your bullet back if you miss.
I’m not from the UK. Returning the game wouldn’t be that simple for me, hence my comment.