I can certianly see why Canada would be at the tops of this list, the Canadian assault on Vimy ridge is one that has certianly deserves mention, Epic, simply epic. Of course, their counter attack in Belgium at Ypres in the face of a German gas attack, cant go unmentioned, full credit to them.
I think the German Sturmabteillung, and their descendants the Stormtroopers, were some of the best formations not only in the German amry, but in the world. However, I would be remiss if I did not mention Paul Von Lettow-Vorbeck and his determined group of east african (Tanzanian) Askari schutztruppen, who waged a very spirited and determined guerilla campagin against the Allies, and is the only German commander who was never defeated in battle.
Another very impressive allies was the American 93rd division and their black troopers, the Harlem Hellfighters of 369 regiment.
And this really only scratches the surface.