Word processor (tie): Quickoffice Pro HD
Almost everyone needs to work on Microsoft Word files, and Quickoffice Pro HD lets you do much of the editing you'd expect, including formatting. Although you can't apply paragraph and character styles to text, Quickoffice does preserve the ones already in your documents. You also get search and replace, and direct integration with various cloud storage services (sadly, not with iCloud). Plus, there's a Business App Store version that allows for content management by IT. But Quickoffice is not savvy about layout-rich documents, nor can it work with embedded hyperlinks.