For the developers here, top on the list of things I'd love to see on my DS:
- NetHack. Perhaps the greatest game of all time; many of its fans have been playing it for over a decade. And it's the one thing that will keep me using my PalmPilot (when on the road) until it appears on the DS.
- An Apple II (preferably, Apple //e) emulator, with a decent onscreen keyboard, and an emulated disk where I can save my files. That'd be lots of fun, since it opens up a form of development I can take with me, and also lets me play great classics like Sabotage.