Why think about adding tasks, managing lists, and getting drowned in contexts and tags when you could just have a Dropbox enabled whiteboard for everything you need to get done? TaskAgent is the minimal to-do manager that you'll want if you'd like the ability to easily share tasks in a readable format via text files (it's that simple), and you'll never be outta sync across your iOS devices or Mac.
You can create multiple lists for work or play, add items, and simply tap them to check 'em off. Adding to-dos couldn't be simpler, and with some basic know-how, you could even format a text file in Dropbox to automatically sync longer lists to your iPhone. How cool is that? The developer has told me that he'll be working on improving the text formatting for the next update to allow for some wiggle room, simplifying the process even further! It's not just the Mac and iPhone that are getting love here: you'll also have access to all of your same tasks via the iPad. The stacked paper view looks great, and of course you can utilize the iPad's portrait keyboard to full effect for easier note insertion. Support for the landscape orientation will be added in a future update.
For the next 48 hours, TaskAgent is only a $1.99 (soon to be $2.99) for a universal iPhone and iPad client. For the Dropbox sync alone (and the ability to work in a universal text file), I'd recommend this if all you're looking for is a basic list that's fast and easy to use.