The trickiest American species to identify.
 

-Scaup Ducks, Lesser and Greater
-Barrow's Goldeneye Hens from Scaup Hens
-Pintail Hens
-Widgeon Hens
-Blacktail Deer from Coastal Deer
-The Grouse and especially the Ptarmigans
-Timber Wolves from Gray Wolves

Male birds and waterfowl are often easier to recognize than females.

Uh, you realize this is the whitetail forum right? Not one of the species you mention are whitetails and only one of them is even hoofed big game.

Sorry, there is no GENERAL, MISC or ALL-SPECIES hunting forum on this site that I am aware of.

Is there a better place to talk about identifying many different game species or hunter knowledge in general?

Speaking of whitetails, they are not hard for me to identify at all by picture.

I can't tell a buck jack rabbit from a doe jack rabbit.
Is there a trick to telling the difference quickly in the field?

:)

Easy. Them bucks got horns! Ain't you seen all the mounts for sale to the tourists from back East? Now, cottontails, snowshoes and pine squirrels are a different matter. Ya got to lift the tail on those and them suckers is fast!

In terms of well-known animals, I'd say the most difficult ID jobs in North America come from immature gulls (specifically of the Herring Gull "family").

I have no idea,I've never seen any of them.

The only way I would see one of these at home is if it got lost and the only way to identify it would be by the funny accent.