If you mean the movies, then I like the Battle of Pelennor Fields best. It makes some amends to Eomer for his getting left out of the Battle of Helm's Deep (which he WAS IN in the book). Though most viewers focus on the anti-elephant feats of Eowyn and Legolas, I thought it was cool how Eomer's businesslike spear-throw ended up stopping TWO of the mastodons.
Any reader of the book knows that the Army of the Dead only helped Aragorn on the southern edge of Gondor; their stopping the pirates was enough for Aragorn to release them, and he had living warriors to carry on from there--fellow Rangers, and local recruits. But accepting the "reality" of how PJ imagines things happening, an interesting thought arises:
Why did the Nazgul take no action to stop the Army of the Dead? The Nazgul were obviously the only servants of Sauron on the scene who would have had any chance of turning back Aragorn's ghost-soldiers, so why DIDN'T they at least attempt it?
The way I interpret it, Sauron didn't care if ALL of his own mortal troops present then at Minas Tirith were killed--provided enough of them survived long enough to kill the good guys' leaders, including Gandalf. (Sauron himself would surely have been immune to anything the Dead could do, and he only cared about himself.) I think that the Oliphaunt which Legolas ended up slaying was definitely ordered to go after Aragorn, on the guess that if Aragorn died the ghost-soldiers would stop killing Sauron's forces and vanish. This brings up another thought. None of the Oliphaunts/mastadons were shown as being attacked by the ghost-soldiers until AFTER Legolas killed the one that was menacing Aragorn. What this suggests to me is that, before coming to Minas Tirith, Aragorn had instructed his undead troops: "In order to avoid killing anyone on OUR side, you must attack ONLY those types of beings whom you see me, Legolas or Gimli attack." Thus the Dead left the Oliphaunts untouched until the sight of Legolas attacking one showed these beasts to be fair game.