CryptoTE - CryptoTE is a text editor with integrated strong cryptography.
GitJournal - Manage your Notes from any Git Repo.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Category Tabs for Google Keep - Better organize your Google Keep Notes
Daybreak - An intelligent to-do app that learns when to remind you
Calendar Note by Enex - Calendar Note app allows users to view the calendar so they can write notes and memos according to dates to get alerts about tasks.