I'm mostly going after some indie titles, myself. Kerbal Space Program, Shovel Knight, Shelter 2, Spelunky, Binding of Isaac: Rebirth, to name a few.
A couple of Steam essentials everyone should have are Skyrim, the Portal games, and Borderlands, if you have friends to play with. Some of my all-time favourites are Hammerwatch, Terraria, Dustforce, BioShock Infinite, and Rogue Legacy. Also pick up the Humble Bundle - this one is particularly amazing. For better or worse I already have most of those games but I might pick it up anyway and get some nice gifts for nice friends.
Lastly, I'm currently hooked on Forge Quest. It's a pretty awesome action RPG similar to Spiral Knights but without the grinding and whatnot. It evidently takes A LOT of inspiration from the Zelda series.