I mostly use 1Password on my Mac to generate and save passwords and logins for websites. But on my iPhone and iPad it makes for a fantastic way to keep notes and other top-secret info safe and secure. And now that it has free cloud syncing via Dropbox (which works perfectly), 1Password just became that much more useful and vital to me.
With the amount of shared information I keep between my iPad, iPhone, and Mac, apps which sync via the cloud are becoming a necessity while apps that don’t are quickly becoming so cumbersome to maintain they’re almost useless.