For me it's the Charge of the Rohirrim at the battle of the Pelennor fields when Theoden makes his speech to his riders:

"Arise, arise, Riders of Théoden! spear shall be shaken, shield shall be splintered, a sword-day, a red day, ere the sun rises! Ride now, ride now, ride! Ride for ruin and the world's ending! Death! Death! Death! Forth Eorlingas!"

Just typing that gave me goosebumps.