Hotline Miami is on sale for $4.94 / £3.44 / €4.44 at Get Games.
This game uses Steamworks, so Steam activation is required.
Buying from GG also gets you a free exlusive the “EXPOsed level”.
What’s interesting about this game is the fact that it was created with GameMaker: Studio. I actually own both. Don’t ask me if they’re installed though ;).