You do not mention any lenses, but Nikon has some pretty spiffy lenses that would make life pretty fun. The new 70-200mm f/4 VR-G seems like a sweet lens.
The new 85mm f/1.8 AF-S G is perhaps *the* sharpest, best-resolving non-macro prime or zoom lens in the current Nikon lineup, and it is light, small, and fairly unobtrusive, and has such AMAZING shaprness that it allows pretty good cropping-in with plenty of sharpness--especially on a high-0desnisty, high-megapixel count sensor like the 24-MP one in your D7100. The new DxO Mark tests of 72 lenses on the Nikon D600 and D800 (same,exact lens samples, same models of course) show that the 85mm 1.4 and 1.8 G are basically, the *best* lenses on those 24- and 36-MP cameras, followed closely by the new Sigma 35mm f/1.4 AF lens, which is in third place, and FAR above many other lenses costing twice as much.
For the money spent, the 85mm f/1.8 G-series Nikkor is an AMAZING value. I am enjoying mine more and more.
Now that we have 24-MP cameras and an affordable, amazing lens like the 85/1.8-G, it's possible to shoot "loose", then crop-in later, and get amazing shots.
I have a D7000 and these are accessories that I enjoy. 1) SB700 Nikon Flash (great flash) 2) Nikon Battery grip (never leaves my camera) I am assuming that it came with an 18-105mm lens, you might consider something like the 70-300 VR zoom and for low light the 35mm f/1.8 prime works great for me.
I'll second the MB-D11 grip (and an extra battery for use in it), SB-700 speedlight, and 70-300 lens. In addition I'll add that if you do any editing on your shots get a hardware monitor calibration device. No more guesswork, well worth the cost. Some equipment to inspect and clean your sensor (yes, you will need it soon).
Once you get the SB-700, get a Demb Flip-It Reflector and an off-camera TTL cord.
If you shoot any birds or wildlife, a 1.4x teleconverter
If you want to shoot macro, some extension tubes.
If you want to get the weight off your neck, a Black-Rapid R7 camera sling