itch.io - An online game marketplace and community.
GameDatum.com - A platfrom of free online games. A list of all the available online free games from various producers online.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
Mitch - The unofficial mobile app for itch.io
Ubisoft Club - Ubisoft Club app enables you to get updates about your favorite games timely.
Enjify - Enjify is an online gaming e-store that enables you to buy games for multiple platforms like Nintendo, PlayStation, Xbox, and Steam.