I'm no developer, so I can only hope a developer creates the apps I'd love to have.
1. A full-fledged finance app, quick entry, charts, etc, that all syncs to an online service when I want it to (there's Mint.com, but that's not available in Japan, and MoneyStrands, but I must sync everytime I open the app, not great for on-the-fly entry.
2. Diplomacy Online - great game!
3. A simple Rotten Tomatoes app, shows synopsis, review summary, tomato meter, and average rating. Checking Rotten Tomatoes via Safari takes a long time due to graphic heavy pages, and 3G poor reception in some video rental shops.