Good Gear Guide
In pictures: 15 must-have iOS apps you can't get o...
iA Writer (iPhone, iPad and iPod touch)
The iA Writer app is about as simple as a text editor can be. It saves your writings in .txt files with no formatting. It automatically saves and syncs with iCloud and Dropbox. It auto-names files and lets you change them as you wish later on. The iA Writer keyboard has commonly-used punctuation keys on its main screen so you don't need to swap back and forth between keyboard screens, and it also has forward and back buttons for quick navigation. Text-editing apps are available for all mobile platforms, but iA Writer is one of the cleanest, simplest and most functional that I've used.
In pictures: 15 must-have iOS apps you can't get on any other platform