Awesomenauts is a really great, charming, and unique MOBA on Steam that's definitely captured my heart. It's stylized like a Saturday morning cartoon, and each character has their own theme, and a "Killing Spree" remix that plays (Only for you!) when you start doing really good.
Another really good Steam game, I think, is called "Don't Starve", it's a really stylish, uncompromising, and unforgiving survival game. You're dumped into the middle of nowhere (Third person!) as one of 10 characters, you have to survive between health, hunger, and sanity. You have to be careful though, if you don't have one of two ways to revive yourself, when you die.
Your world gets deleted as well.
And there's no option to turn it off!