You wouldn't think that Half-Life 2 and Hotline Miami would make great bedfellows, but hey, sometimes two unlikely things come to make a great combination.
Mixing the two titles together, developer Thomas Kole has created a bloody top down game, set against head crab zombies and gravity guns. It's a pretty fun mix. The developer says he made it because he likes both franchises also just for the game design experiment. You can play it here.
To get an idea at how it works, take a look here: