I've just acquired an R4 card for the Nintendo DS. The notorious device (now one of many) that lets you run unlicensed software on the machine - including pirated software, naturally. Funnily enough the piracy side of it holds no interest for me; the reason I got it was for POWDER, Nethack DS, and Lone Wolf DS.
It's fair to say I'm over the moon with it. I've taken to Nethack much more than I ever managed to on the PC (something about the interface on PC always felt clunky and opaque to me), POWDER is just plain lovely. It's as harsh as any Roguelike but is presented in a wonderfully cheery way, with bold, colourful graphics. Lone Wolf is a real treat, and I very much hope the developer continues and translates more of the saga in this form.
There are quite a few homebrew projects bubbling away at various levels of completion. Some very interesting indeed - most especially the Dungeon Master port which is currently in very early alpha build. To be honest though, I feel I've more than justified my investment by having a couple of great Roguelikes on there - games that will hold my attention far longer than any official DS title could ever hope to.