The crowner of that crowning moment is when you finally fight your way up an defence emplacement, kill the gunners on top and turn a machine gun against the other emplacement and let the Germans there see how they like being mowed down!
Driving the King Tiger in Allied Assault counts more as a Crowning Level of Awesome.
The ending of the first game. Reprogramming a V2 rocket and firing it at its own launch facility was pretty tight.
The ending of the second game tops it. One-Woman-Army Manon single-handedly fights her way out of an ambush involving an entire armoured column, then saves Paris by causing two German trains carrying explosives to crash into each other!
Warfighter's penultimate level: Preacher pretty much singlehandedly takes down an entire ship of terrorists using nothing but a pistol and whatever weapons he ripped from the enemy's dead fingers. The purest combination of One-Man Army, Roaring Rampage of Revenge, and Unstoppable Rage you can ask for.
One behind the scenes: the 2010 remake was going to have a scene where one of the Tier 1 soldiers was killed. Keep in mind they have the absolute best of the best helping in development. A quiet word from one of them later and the scene is removed.
The opening cinematic of the first mission of European Assault. A battalion of British commandos aboard a captured German boat trying to sneak into the St. Nazaire harbor at night, the tension the men are feeling so thick it's almost visible. Then suddenly, the Germans open fire and in the midst of the shooting, the commando leader orders the Union Jack hoisted and declares We'll ram it down their throats!!" right before the boat rams the docks at full speed. Now THAT is how you start a game.