Spelunky, Risk of Rain, Hotline Miami and the like used it for development:
via Moraven
Sale
Are you an aspiring game designer, artist or programmer looking to for a way to take your work to the next level? Become a Pro and take advantage of our GameMaker: Studio Professional sale!
For a limited time YoYo Games is giving all GameMaker: Studio Standard users the chance to upgrade to GameMaker: Studio Professional for only $35.00! Go to our Checkout Page and enter your GameMaker: Studio licence key to get started.
If you don't already own a copy of GameMaker: Studio, for a limited time, you can now get your own GameMaker: Studio Standard license, completely free! To get your copy of GameMaker: Studio Standard simply download the Free Version and follow the instructions that appear inside.
This Sale ends March 2, 2014, so take advantage of these offers before they are gone!