iPhone: While iOS isn't lacking for great task manager apps, Wiselist carves out a niche of its own with a gorgeous UI and a unique blend of features.
The app isn't just a typical checklist app; it brings plenty of powerful features to the table that give you a lot of flexibility. The app is centred around "Wiselists", which contain all the data you need for a given project. You can add long text notes, checklists and even files from your Dropbox or camera roll to really flesh out each list with everything you related to a project. If you have multiple lists related to the same idea, you can categorize them with different tags, and assign each tag a custom colour to make them easier to visualise on the main screen.
There's a lot going on in Wiselist, and the app does take a few minutes to get used to, but it's a great value for its sheer flexibility. Unfortunately, it doesn't sync with any web or desktop clients, and it's not even available for the iPad right now, so this probably won't replace Wunderlist or Omnifocus for serious productivity hounds. At $0.99 though, I think it has a place in a lot of peoples' workflows as a powerful replacement for Apple's Reminders app.