These sites reveals games from steam, epic games, etc. which are 100% off, basically Free.
1. Steamdb - only shows games from steam. (Alternative: Steamdb.v2 - gives more details)
2. IsThereAnyDeal - offers 100% off games and not only that, there are also vouchers and bundles.
3. SteamSearch - from the site itself, it filters the lowest price which includes 100% Off
