This version of L is pure distilled awesome from start to finish, to the point that Twilight has to be even smarter than Light was in order to take her down.
During a rescue mission the police team encounters a golem sentry and are forced to spend several days hiding behind a boulder, staying undetected while waiting for a chance to present itself. Zecora, who is their guide, helps them pass the time through storytelling - staying without sleep for several days, and all that time speaking in rhyme.
Since she's Kira, Twilight's moments of awesome also tend to border on the Moral Event Horizon. That said, the way she wipes out a whole EBI unit and engineers Rarity's murder/suicide in order to earn her way into L's team are both impressive bits of chess mastery.
Twilight gets a non-Kira related one during the fight with the first golem, when she manipulates the weather around its arms to blast them off.
A sadly Offscreen Moment of Awesome: when Mer tried to coerce the Apple family into becoming the Third Kira, Granny Smith refused to let her grandchildren become killers. As AJ puts it, she stared down a God of Death and said no. This got her killed, but it's still awesome nonetheless.
Rainbow Dash unloading on Applejack upon hearing her motives for acting as Kira. She tells her in no uncertain terms that while she may fear death, there's no way she would want her best friend to become a killer for her sake. It's really refreshing at this point in the story that at least one of the Mane 6 refuses point-blank to compromise her moral integrity.
The sting operation in chapter 29 is very impressive, as is Applejack actually managing to hurt Princess Luna upon being exposed as the Third Kira.
Derpy, of all ponies, is the one who brings down the Third Kira by summoning a massive thunderstorm to slow down Applejack, then beating her to a pulp! "Never kill again!"
Twilight anticipating that her Memory Gambit might be foiled and adjusting her plan accordingly to end up on top of the inevitable Gambit Pileup.