Presentation editor: Keynote
Simply put, Keynote is an amazing slideshow editor. I prefer it over PowerPoint even on the Mac, and on the iPad, it works beautifully, even when creating complex slide transitions and element effects. If someone tells you an iPad is just for content consumption, Keynote is all the refutation you need. And its iCloud compatibility can be a real life-saver, ensuring all your devices have the current documents. A bonus is Apple's free Keynote Remote app for the iPhone and iPod Touch that lets you remote-control a Keynote presentation on your Mac or iPad.