My favorite has to be Artillery. You sit and down and whittle away at the enemy from afar whilst other units lay in wait to defend the artillery and eventually advance. If you have more artillery then the enemy then you're almost guaranteed a win.
I usually see France and Germany get chowed up pretty early in those games and I almost never play as them. Probably because they're surrounded and are prime targets for people roleplaying as the Soviet Union and stuff.
Something funny or interesting to note is that Fidel Castro died on the birthday of right wing Chilean dictator Augusto Pinochet. He was well known for pushing communists from Helicopters as a form of execution.
I think a map dedicated to the eastern front in 1941 with all the powers would be interesting. Have the two major powers of Germany and Russia along with smaller nations like Hungary and Romania.