Everyone likes discounts, but they carry pain too, devaluaing the used-market price of all my gear. What has never been discounted to my knowledge? My trusty Zeiss lenses (for Canon or Nikon).
Canon lens rebates expire Nov 22.
See also Leica M discounts. Update: the lens rebates on Leica M are now up, see the handy links on the Leica gear page to find any particular lens.