In one book, he manages to use a very small gun to shoot inside his opponent's gun, destroying it from the inside.
In Dalton City, we are introduced at the beginning of the story to a corrupt, outlaw-populated city, where a corrupt saloon owner is ruling and sheriffs are constantly either getting killed or intimidated into leaving, with the saloon owner collecting their stars as trophies... until Luke arrives as the new Sheriff. He then puts an end to the corruption in the city in one night, by defeating and taking the Saloon owner hostage.
In Billy the Kid, Billy tries intimidating Luke by demonstrating his speed: he lets a candy fall from his hand, then draws his gun before the candy hits the ground. Luke's answer? He lets the candy fall from his hand, draws his gun, put it back in its holster, and then catches the candy before it hits the ground.
Luke (eating the candy): It's more hygienic that way.
In a similar fashion in another book, a bounty hunter sent to kill Luke tries to impress him by throwing a coin and shooting right in the middle of it. Luke reacts unimpressed, causing the bounty hunter to to do the same trick with four coins, only for Luke to mock him about how this is a waste of money. Eventually, the bounty hunter throws a card in the air and cut it in half by shooting at it.
Bounty Hunter: So? Was that lame or a waste of money?
Luke: No, but you just used the last of your six bullets. You are under arrest.
In Calamity Jane, Jane takes part in an arm wrestling with the main villain's Dumb Muscle, Baby Sam. As they start, it seems like she is losing, and everybody places his bet on Baby Sam. Then, at the very second everybody has placed his bet, Jane reveals she wasn't using her full strenght, and easily wins in one move of her wrist.