Although Preston is the only one we see doing any actual Gun Kata: Partridge is deliberately letting Preston do all the work, Brandt's only on-screen shooting is with an assault rifle, and none of the other Clerics bother.
Bodyguarding A Badass: In the final fight, Brandt guards DuPont even though, after Preston cuts off Brandt's face, it becomes clear that DuPont is a master at Gun Kata.
Boomerang Bigot: DuPont wants to destroy all sense-offenders, despite the fact that he is one himself.
Broken Faceplate: When a mook's visor is shattered they invariably collapse and die; it's due to being shot in the face, or a pistol lethally slamming into the Sweeper's skull after passing through the faceplate.
Bullet Proof Human Shield: At one point, Brandt machine-guns a sense offender who is grappling with Preston without killing him too.
Chekhov's Gun: Where Preston literally hands his gun to Brandt for later exploitation.
Chemical Messiah: The drug Prozium makes people emotionless. The top brass sell it as a solution to man's tendency to war and strife. It isn't addictive, though going off of it can be difficult for people because it's almost like going on a drug, with a flood of emotions that are hard to control or hide.
Church Militant: Despite serving a secular state, the Grammaton Clerics use the trappings of this trope.
Some of the quasi-religious vibes are a bit more subtle: Though it also sort of resembles the Nazi swastika, the symbol of the Librian regime is most similar to the type of cross seen on the coat of arms of the medieval Kingdom of Jerusalem, or the "decapitated cross" of Brave New World. Moreover, "Tetragrammaton"note loosely translated as "the four-letter word" is an euphemism used to refer to the name of God.
The Cobbler's Children Have No Shoes: The Tetragrammaton Clerics are tasked with rooting out and apprehending or killing Sense Offenders. Preston, stated as being one of the best Clerics, fails to realize that his entire family, both partners, and his boss are all Sense Offenders. It's clear that his reputation is based on his combat skills rather than his ability as a judge of character.
It is stated very early that Preston's high rating is due to his talent at finding emotional content material, no matter how well hidden they are in the sense offender's lairs, not his obviously lackluster ability to actually find the people he's supposed to be hunting.
Real Life Writes the Plot: According to the DVD commentary, the whole film was shot on a tight schedule, and the final confrontation scenes in particular were made in a rush. They actually had planned for a legitimate fight scene between Preston and Brandt, but they simply couldn't get Taye Diggs available in time to do the scene, so they did a pragmatic move and turned the whole thing into a Single-Stroke Battle, with a body double standing in for Diggs.
Faceless Goons: The Sweepers, who wear either riot gear or storm-coats, but almost always wear closed helmets.
First Time Feeling: Hits Preston hard, not least because, at the time, he's found and is listening to an old vinyl album of Beethoven's Ninth Symphony, one of the most tremendously moving pieces of music ever produced by the human species. Even the script describes this introduction to human emotion as 'unfair'. (But it does a lot to explain his subsequent actions.)
Flat "What.": The reaction of the Nethers captain to seeing two of his men killed with their own shotguns.
In the beginning of the film, Brandt comments that he needs to stop by an Equilibrium center to have his dose adjusted, meaning he's either under-medicated or over-medicated.
John's daughter playing with her cereal near the beginning of the film foreshadows that she is no longer on Prozium, as does the fact that his son gets annoyed with her hint that he isn't on it either.
DuPont is teaching the Gun Kata class early on because he himself is a master practitioner.
Freeze-Frame Bonus: Preston's Beretta shot flares look like the Tetragrammaton cross logo. The producer himself has stated that it was mostly a wasted effect, as few viewers noticed it.
Gas Mask Mooks: The incinerator personnel at the Hall of Justice. In scary black Soviet PBF gas masks.
Preston rushes to the execution chamber to prevent Mary's death, but arrives seconds too late.
Preston's revolution was a trap of the authority.
Humans Are Flawed: The entire reason for the plot was because human emotions were a flaw and the cause of 'man's inhumanity to man.' The ending, while portrayed positively, never exactly comes clear on whether restoring human emotion is a good thing.
Idiot Ball. The Big Bad lets Preston, the highly trained Cleric who has killed multiple Faceless Goons and proven himself a serious threat, walk into the main headquarters without even bothering to search him for weaponry. He then tells Preston the master plan and as soon as his villainous monologue ends, Preston pulls out some firearms and fights his way to the boss's room. In a deleted scene, it would've shown earlier that the metal detectors are at the next door Preston walks through after taking the lie-detector, which raises the question of why they put the anti-gun security measure there instead of before the room they planned to spring their trap in. Of course, since Gun Kata requires emotional control, and they figured Preston was off his meds, he shouldn't have been able to use Gun Kata.
Imperial Storm Trooper Marksmanship Academy: Averted. At first, it seems this is the only why Preston wasn't immediately killed when he went through the door at the sense offender hideout in the beginning. However, statistically the first man into a room is one of the safest in the opening seconds of an engagement (the Second man in line is usually the first one to buy it) if his entrance is hard and fast enough. Preston slammed through the door all the way to the middle of the room in about a second, by the time the guys in the room realized he was there, the lights were out and they couldn't really shoot him without killing each other.
Invincible Hero: Preston. The director finds it boring when the villain "gets a few good licks in" on the hero because he has no intention of subverting audience expectations with a Bad Guy Wins ending, and thus, there's no point in making it seem like the villain has an advantage at all when the result is a foregone conclusion. He does acknowledge that not everyone likes this approach. And yet, for all his physical invincibility, he turns out to be incredibly emotionally vulnerable.
Kick the Dog: The Sweepers are shown gunning down fleeing and captured Resistance members, and dogs.
Late Arrival Spoiler: "Not without incident." The trailer doesn't provide enough context for it to be a real spoiler, but you'll know where it's coming in the movie, and it was clearly intended to be unexpected.
Licked by the Dog: Literally; several minutes after Preston cries at Beethoven, a puppy licks his face and brings out his compassion — so much so, he ends up killing about eleven guys after he decides to keep it.
Near the end, DuPont echoes the Yeats poem Partridge was reading near the beginning: "You're treading on my dreams."
Before shooting Partridge, Preston mentions the anger and hatred felt by sense offenders. Partridge replies, "A heavy cost. I pay it gladly." When DuPont asks Preston whether killing a feeling human is worth the price, guess how Preston replies?
When Preston starts following Partridge's path, he repeats some of his excuses. "They miss things, sometimes..."
Mobstacle Course: Preston does this at least twice, one time without a real purpose besides just wanting to be alone.
Mondegreen: When Preston doubts the wisdom of overthrowing the government, he says "What about war, the everyday cruelties that are all gone now?" Jurgen's response is, "Replaced by the Tetragrammaton?" Many think he's saying, "Replaced by a touch of grammaton?"
Mouth of Sauron: Libria dictator "Father" is all over the television, but almost no one meets him personally. Vice-Council DuPont is explicitly described as "Father's Voice." Turns out to be a subversion: the real Father died years before, and DuPont is actually running things while pretending to be the Mouth of Sauron.
My God, What Have I Done?: When Preston rewatches the recording of his wife's incineration, this time being able to feel. His face becomes a mask of complete and utter horror when he sees how he had just stood then, uncaring and cold, while she had been sent to a gruesome fiery death.
Earlier than that, the first time he kills a man after he goes off Prozium.
Never Trust a Trailer: The trailers make it seem like Preston's wife was arrested recently and his motivation is pure revenge.
Offhand Backhand: Pretty much any shot Preston makes falls under this trope, since Gun Kata eliminates the need to actually aim.
Pendulum War: The minute Preston stops the broadcasts from Father, the previously completely ineffective sense-offenders Zerg Rush the Sweepers with zero casualties observed.
Pistol-Whipping: The scene where Preston tries to let the sense-offenders escape. The resulting beatdown leaves several Sweepers dead.
Plot Hole: Supposedly, Preston swapped his government-issued (and personalized) gun with Brandt's to frame him for killing the Sweeper patrol. The swapping scene clearly happens after the killing scene, and in any case he used two guns in the fight and only swapped one. Some people think this hole is obvious and unforgivable. Others forgive it in order to enjoy the rest of the film. Still others come up with bizarre, elaborate justifications for why it makes sense if you think about it hard enough, usually fueled by an earlier scene where Preston hands Brandt a gun. The actual explanation is that the narrative was shuffled in editing to improve the pacing, and the director decided to let the plot hole slide.
Shadow Dictator: Inspired by 1984, "Father" is the mysterious and omnipresent dictator of Libria. Though we do see broadcasts featuring him, They are faked, since the original Father died, and Du Pont was chosen to replace him.
Straw Hypocrite: DuPont and Brandt aren't on Prozium. In the commentary, the director explains that this was done because most people assume that breaking their own laws is one thing all tyrants have in common, and he cast Taye Diggs as Brandt partly because of his giant smile.
Straw Vulcan: The ideological mainstream is so set in the belief that emotion is at the core of "man's inhumanity to man" that any attempt to evoke feelings in oneself or others is punishable by summary execution.
Preston has some sort of device up his sleeves (literally) that will reload his pistols for him when they run empty.
During the final shootout, Preston is confronted by a hallway of machine-gun Mooks. He throws two magazines of ammunition halfway down the hallway, then starts shooting, running out of ammo exactly where the two magazines landed, reloads and continues gunning 'em down.
And the one guy assuming his Walther WA2000 is a shotgun, racking a nonexistent pump.