Unity - The multiplatform game creation tools for everyone.
Quip - Quip is the modern productivity suite that simplifies your life and helps your team get work done faster.
Godot Engine - Feature-packed 2D and 3D open source game engine.
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.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.