If you're looking for a Sigma Art lens, most of them are now getting a US$100 discount for the Thanksgiving Holiday.
DX users should pay particular attention to the 18-35mm f/1.8 and 50-100mm f/1.8 lenses. These are great lenses for the D7500 and D500, though the D500 can't focus with the outer sensors on the 18-35mm reliably (just use the center five columns).