Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Working Copy - The powerful Git client for iOS
OneNote - Get the OneNote app for free on your tablet, phone, and computer, so you can capture your ideas and to-do lists in one place wherever you are. Or try OneNote with Office for free.
Source iOS - The best git client and code editor for iOS.
Standard Notes - A safe place for your notes, thoughts, and life's work
CodeHub - CodeHub is the most complete, unofficial, client for GitHub on the iOS platform.