Hybrids always interest me. Here's a few rounds of hybrid waterfowl for your enjoyment:
A hybrid American x Eurasion Wigeon (Anas americana x Anas penelope), found by Paul Hurtado, Shawn Billerman, and myself this past winter on Cayuga Lake.
A series of photos of a "Brewer's Duck", a presumed hybrid Mallard x Gadwall (Anas platyrhynchos x Anas strepera), also in the Cayuga Lake Basin.
A birdforum thread on an interesting hybrid of unknown eurasian duck species.
A presumed hybrid Hooded Merganser x Bufflehead (Lophodytes cucullatus x Bucephala albeola) with discussion on the Frontiers of Identification listserve.