* Autodesk SketchbookPro, 50% off an annual subscription to the leading 2D digital sketching software. Code: THANKS17
Last I heard, it was credit card only, and a recurring payment, though. Which may be a deal-breaker for many.
* Corel Painter Essentials, for £24, at the Corel store. Also discounts on Corel Painter 2018.