If ou want seafood, Mariscos Chihuahua is the place. They have Guaymas shrimp, oysters, and fish, and even though the menu is somewhat limited, everything they do is awesome. Try the shrimp culichi and see if you can stop before it's all gone...
Not only that, the interiors of the various locations are too much, in an awesome way!
That's a loaded question and low key is hard to define but here are some options...
Try Zivaz for really good Mexican food with a twist - http://www.zivaz.com
For Malaysian food - try Seri Melaka or Neo Melaka
Rocco's has the best pizza in a divey setting
Brush Fire BBQ is really good