The Fords of Norway - As Denmark, capture the American city of Detroit with a Norwegian Ski Infantry unit.
Oops. - Kill at least 4 of your own units with an Atomic Bomb.
The Schlieffen Plan - As Germany, make Antwerp or Brussels declare war upon you by trespassing in their territory with Great War Infantry units.
HAWAII! - Playing as America, found Honolulu before Polynesia does (side note here: this is 9999999999999999% impossible unless you use IGE)