The iPhone's Safari browser has a Google search bar built right in, so why bother with a separate app? Three words: voice-powered search. Just hold the phone to your head, say your search terms ("How do magnets work?"), then let your jaw drop as the app instantly produces spooky-accurate Google search results. Once you start using this, you'll wonder how you ever got along without it (kind of like Google itself). While you're at it, check the equally miraculous Google Translate.