Do any aircraft possess washed-in wing characteristics?
According to Wikipedia, the Grumman X-29 had washed-in wings, as its considerable forward wing sweep gave it a strong tendency to stall at the roots.  As the wing roots on a forward-swept-winged aircraft are located aft of the wingtips, a root stall on such an aircraft would cause a strong pitch-up tendency, so the X-29's wings were washed in to mitigate the root-stall tendency.