If you are looking for the latest active redeem codes for All Star Tower Defense X to get free Gems, Trait Burner, Capsule, ...

You can only get Radioactive Coins in Escape Tsunami for Brainrots during a Radioactive Event, of which, there are a couple.

Cookie Run: Kingdom developers often release codes that you can use to claim free rewards such as Crystals, Jellies, EXP, ...