I kind of forgot all of the things I suggested...though you could add a text reader (if I haven't suggested that already). I am kind of at a loss of what else to suggest...I mean it isn't like I've been able to see most of the other stuff yet...
(contact list, text reader...I guess I did suggest that earlier..., stopwatch, calculator, virtual piano (just a screen with a piano and you press on the touchscreen to make notes come out is fine...), and the tip calculator)
I'll re-suggest at least a part of the DiagnoSe app because I don't really think the DiagnoSe app I'm thinking of would be that hard since all it really does is wait until you press something and show that you pressed it...(well maybe other parts might be hard to do, but button testing shouldn't be).
Apart from those suggestions, you could add RSS reader, dictionary, wiki app, option to change languages, maps,
stereogram app (since I can't get this one to work on my flashcarts...), e-mail (?), blogging (?), virtual pet (Tamagotchi much xD, though I'm hoping for a digivice), spreadsheet app, flashcard app (for studying), IRC app, update via wifi (?), edit wifi settings (?), screenshot by holding a button (like moonshell2), lock with a passcode, metronome, and that is about all I can think of at the moment.