Simplest notes application.

A-to-Z (A to Z) Notes is a type of notes archive (we also call it reference), with simple, yet highly effective grouping system: all the notes are added to a Letter of an Alphabet.
This way, you can easily find your note, months after you put it there, enough that you know what it is about. We used to have such system on PC, applied as part of the GTD, in the form of folder/files.