Though it is only a small moment Peter finally managing to produce Lux is pretty awesome.
'Moon Over Soho' the magic battle on the rooftops: He threw a fireball at me. I threw a chimney stack at him - that's the London way.
Taking down the tigerman in the stairwell by giving him a facefull of Doc Martens and then surfing down the steps on his back was pretty awesome too.
an In-Universe example, this is Peter's reaction to Nightingale describing how he took on two Tiger Tanks in WWII by himself...and blew them apart.
According to another survivor in Foxglove Summer, Peter is not giving Nightingale enough credit. Taking out the Tigers were the least of his feats. Nightingale is described as being just shy of godlike in that battle.
Lesley managing to produce a werelight at the end of book two.
Although we don't get to see much of it, the battle between Nightingale and the Night Witch in the fourth book. The same book also features Peter outsmarting the Faceless Man and almost capturing him.
So as not to spoil an awesome scene, but said battle between Nightingale and the Night Witch include him unzipping the front of a barn as a distraction so he can walk in the back, doing something that made a cottage look as if it had been hit by a freight train and one or other of the two lifting the entire roof off the aforementioned barn and then bringing it back down. All of this without even creasing Nightingale's suit. Suddenly it makes much more sense why Nightingale was on rearguard at Ettersburg.
During the climax of Broken Homes, Peter outsmarts the Faceless Man during their Rooftop Confrontation. The Big Bad jumps off the soon-to-be-blown-up building, using a spell to soften his impact. Peter jumps him and clings on, knowing that to shake him off, the guy would have to stop chanting, thus laying them both out for a rather rough landing, after which Peter goes to town on the guywith his trusty size eleven's. And then Leslie finally gets to use her taser...
Foxglove Summer has Peter using a magic cane on a unicorn. The unicorns were terrifying for pretty much the entire book until that point. After that confrontation, the unicorn flinched whenever Peter looked at it funny.
The Hanging Tree has more than a few but one of the best has to be an off-screen moment. Nightingale finally confronts the Faceless Man who attempts to kill Nightingale with a booby-trapped apartment, which is massive underkill for a guy whose combat experience is open warfare against the German military. Nightingale bypasses them and though we don't see it, it's implied that the majority of their fight is the Faceless Man retreating away from him.
William of Tyburn gets one when he hurls a sword from one building to another and nails a sniper right in the heart!