Overleaf - The online platform for scientific writing. Overleaf is free: start writing now with one click. No sign-up required. Great on your iPad.
LibreOffice - Writer - Open-source cross-platform word processor.
TeXworks - The TeXworks project is an effort to build a simple TeX front-end program (working environment)...
Microsoft Word - Microsoft Word is a commercial word document processor for Windows.
Texmaker - Texmaker, free cross-platform latex editor
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.