Eddie Dean shows exactly why the Gunslinger's Creed contains the line "I shoot with my mind" when he defeats Blaine the Mono.
Just HOW Eddie defeats Blaine is a combination of funny and awesome; he does it with a dead baby joke
Although Roland just about tops him by cussing out the Mono right before that. And why wouldn't he? After all, Blaine was built to serve the Old Ones, of which Arthur Eld and Gilead were part. Roland is of the line of Eld. Him cussing the train out is man asserting his dominance over a machine. And Blaine quietens down. Oh, there's so much of Roland's speech this troper uses against Windows Vista...
Jake gets his in the desperate assault on the Dixie Pig.
Susannah's manipulation of a succubus and consequent duel with Mordred Deschain.
Oy doesn't miss out on awesomeness just because he's a billy-bumbler. He, knowing he will die in doing so, attacks Mordred when he tries to ambush Roland and Patrick, saving their lives. Susannah was right to think this:
The bumbler had proved his mettle on more than one occasion and would have been worthy of the title gunslinger, had he but a gun to sling and a hand to sling it with.
"Oy! Eld! Thankee!" And the bow. Definitely a 'F*ck yeah!' moment for this troper.
Roland himself gets several, usually when he shows the reader exactly how he managed to be the last gunslinger.
Everything about Roland's coming-of-age trial: his father previously held the record as the youngest to face the trial, and Roland has him beat by almost a full year; his completely left-field choice of weapon; besting and breaking Cortland Andrus; all done so he can face Martin, the man making a cuckold of his father, as a man himself, and give him a a big helping of GTFO.
Tull. In the first book, Roland, with nothing but his twin guns and badassery, single-handedly kills every man, woman, and child in town. To be fair, it was in self-defense. This is the moment the reader knows beyond all doubt that Roland is not one to be trifled with.
Some of Roland's crowning moments come when he's not fighting. Dancing the rice-dance, showing his diplomacy, and knowing when Jake needs a chance to actually be a preteen boy. That's what makes him a gunslinger... his ability to shoot is only part of the package.
The aforementioned take-down of Blaine the Mono:
Kill if you will, but command me nothing! You have forgotten the faces of those who made you. Now either kill us or be silent and listen to me, Roland son of Steven, gunslinger, and lord of the ancient lands. I have not come across all the miles and all the years to listen to your childish pratting! Do you understand? Now you will listen to ME!
Pere Callahan gets the big one. "Throw it aside! Nasty bauble of the sheep-God, h'row it aside if you dare!" "I needn't stake my faith on the challenge of such a thing as you, sai, And I'd never throw away such an old friend in any case. But put it away? Aye, if you like." Then he forces elder vampires back with nothing more than a a battle aura composed of pure, distilled faith. "GET BACK! THE POWER OF GOD AND THE WHITE COMMANDS YOU!" Badass indeed.
Even Mordred has something of one, in his surviving so long. To paraphrase: He thought he could make it through the day because he'd never have to make it through another.
During a flashback to Tianís grandfatherís past in Wolves of the Calla, a girl named Molly Doolin gets one when she becomes the first and, until Roland and his ka-tet show up, only person to kill a Wolf. She dies almost immediately after.
Molly: THIS IS FOR MINNIE, YOU SONS OF WHORES!
Villainous Valor example: Pimli Prentiss, a seemingly unremarkable character - no more than a guy from Jersey, in fact - successfully lands a headshot on Eddie while mortally wounded, summoning the last of his strength and actually defeating a Gunslinger.