After the new Nikon lens-0nly rebates, Sigma also dropped the prices on some of their Art lenses for Nikon F mount. All Sigma lens rebates can be found here.
Tamron is offering up to $200 off on selected lenses for Nikon F mount plus 10% back in rewards. The Tokina AT-X 16-28mm f/2.8 Pro FX lens is currently $130 off.
Some of those offers are WPPI specials that will expire tomorrow and you may need to add promo code BHWPPI16 during checkout in order to get the discounts.