Muscovy Duck is a large duck found around public parks in nearly every state of the USA and in the Canadian provinces. This is the only breed of domestic duck that is not decended from the mallard, being technically almost a goose. They are also strange in the fact that they do not quack, but make a hissing sound instead. To be polite, there beeks are kind of ungly with a flap of skin cover the top part.

Mulard aka "mule ducks" is a hybrid variety of domestic duck. Most of the ducks on the Funny Farm started out as Muscovy crossed with Mallard ducks.

Rouen is a heavyweight breed of domesticated duck raised primarily for decoration or as general purpose ducks. They resembles a Mallard but they are brighter in colour and larger in size than Mallards. 

Wood Duck is a medium-sized duck. They are about three-quarters of the length of an adult Mallard with the adult male has distinctive multicolored plumage. The female, less colorful, has a white eye-ring and a whitish throat.

Other terms

Tuff or Crest. Growth on top of head. Best example is Afro.