So I picked up a Nikon 20mm 1.8G a while back and I have to say I love it! It focuses super close which gives you some cool perspectives, and lets you take advantage of its bokeh powers.
D600 20mm @ 1.8 1/50 ISO1600
20mm @ 1.8 1/100 ISO100
20mm @ 1.8 1/400 ISO200 (Maternity shoot of my friend. Went a bit creative with the ultra-wide)