Yesterday I was shooting with the D7100 and what I believe to be the best walking-around, all-in-one lens for DX Nikons, the 16-80mm f/2.8-4E VR. It's got a usefully fast aperture, a useful zoom range (the equivalent of a 24-120mm on full frame), image stabilization, some weather sealing, and it's razor sharp. If I could only have one lens to use on my APS-C Nikon bodies, this'd be the one.
.
