Animal Theme Naming: Each of them is code-named for a breed of cat: Abyssinian, Bombay, Balinese, and Siberian. Gluhen adds "Havana [Brown]" and "LaPerm," although unlike the original four these codenames are never used aloud in the anime (they belong to Kyou and Sena respectively)
Cartwright Curse: As a side effect of being Doom Magnets par excellence, nobody in Weiss has much luck keeping girlfriends alive. Yoji has it the worst, but everyone on the team except for Kyou has at least one instance.
Creepy Cool Crosses: A white cross is the team's logo, and they all wear red crosses on their "working clothes" in Gluhen. Both Aya and Youji wear silver crosses with their street clothes (justified in Aya's case, since he's at least shown to read the Bible and talk points on it with nuns).
Flower Motifs: Each of the boys is associated with a particular flower: Aya is red roses, Omi is freesias, Youji is cattleya (a specific type of orchid), Ken is gentians, Sena is pansies, and Kyou is yellow roses.
Four Is Death: Aside from initially having four members, look at the fates of the Fourth Weiss team: two dead, one amnesiac, one in prison, one stabbed to not-quite-death on a street corner, and their boss giving up everything that makes him a nice person.
It's Personal: The Third Weiss team (Aya, Omi, Ken and Youji) all have a fairly plausible reason to want Reiji Takatori dead. Fourth Weiss' new recruits, Kyou and Sena, both have a deeply personal reason to find out what the deal is with Koua Academy. Persia II all but admits he did this on purpose; Persia IV tells Rex outright that he did.
Necessarily Evil: How they perceive themselves, Ken going so far as to state it out loud in exactly those words.
Ragtag Bunch of Misfits: a failed P.I., a disgraced athlete, an amnesiac student, and a very angry young man out for revenge.
True Companions: Played with. It's plain to the audience that the core four care about each other, but they're all so damaged and wrapped up in their own issues that, by the time they realize it, it's too late.
Neither the devil nor death, I am just a murderer.
Adaptation Dye-Job: Went from bright red hair in AAWS and Kapitel to brown in Gluhen. Might be an actual dye job, as most Side B color art gives him back the bright red color, but the one cover art that shows him as he was in the final episode of Gluhen uses the darker color. On the other hand, flashbacks and old photographs in Gluhen show him having the brown hair the whole time, so it's really anyone's guess.
A Man Is Not a Virgin: Fight Fire With Fire goes out of its way to reveal that Aya lost his virginity at 16. Otherwise, Aya shows absolutely no interest in sex - which stands out because Youji, Ken, and Omi do.
Asexuality: Ranjatai suggests this is the case with Aya and makes something of a point of his lack of sexual interest in Shizu.
Badass Teacher: Gluhen: Asami-sensei sees him this way after he stands up to S Class to defend Sena. Her perception is not exactly accurate; although Aya would probably have moved himself to defend any other innocent student in danger if given opportunity, the issue mostly never comes up.
Big Brother Instinct: Compulsively, not just to his actual little sister but also to Taiyou (even though they're the same age), Sakura, Sena, and Yuki.
Big Damn Heroes: Repeatedly. Weiss as a team sometimes manage to play Big Damn Heroes to save the victim of the week, but Aya especially has a way of turning up to bail out his teammates when they're in trouble.
Combat Pragmatist: Best illustrated when Aya pulls a gun in the middle of a sword fight.
Cool Car: His white Porsche doesn't look like much in the original anime's lackluster animation, but is quite snazzy when viewed through the higher production values of Gluhen - something that is possibly helped along by it being a completely different make of white Porsche.
Flower Motifs: His given name, "Ran," means "orchid," a fact played with more than once in the series.
Healthcare Motivation: Aya-chan's hospital bills were a major factor in why he became an assassin, and the primary reason he joined Kritiker: they promised to provide for all of her medical care if he joined.
Relative Error: Omi and Sakura both assume the cute, comatose girl he's caring for and using the name of is his lover, instead of his little sister. In Assassin and White Shaman, one of Ran's coworkers assumes Aya-chan is his girlfriend when she drags him away from his job to buy her something to eat.
Save the Day, Turn Away: He removes himself completely from Aya-chan and Sakura's lives after saving them both from Essett and Schwarz at the end of Kapitel.
Adaptation Dye-Job: Went from dark blond hair in AAWS and Kapitel to a grayish color in Gluhen. As a possible justification: The Takatori family doesn't want it recognized that Omi Tsukiyono and Mamoru Takatori are the same person. Change the color, change the style, instant unrecognizable look.
Luke, I Am Your Father: Oh, where do we start? Let's see. Two of Weiss' targets are his older brothers, the man behind it all is his father, his potential love interest, Ouka, is his half-sister—but wait! His mother was sleeping with her brother-in-law on the sly, so his father is really his Uncle Shuichi—AKA Persia. So Ouka is actually his cousin. Parodied in the "Wish A Dream" CD drama, when Omi has a nightmare that not only is Ken his older brother but Youji is his father and Aya is his mother.
Manipulative Bastard: In and following Gluhen: "Hey, I know how I'll find Epitaph! I'll hire a confused, ticking-time-bomb of an amateur, teenage assassin whose mother murdered the rest of his family, and let him run wild. If he screws up enough times, they won't be able to resist the bait!"
Meaningful Rename: Shuchi Takatori renamed Mamoru Takatori "Omi Tsukiyono" after rescuing him from his kidnappers. Tsukiyono Castle was the vacation home of the Takatori family and as of Dramatic Precious is the private residence of Saijou Takatori, the first Persia; "omi" means "retainer" or "servant."
Odd Name Out: Hirofumi, Masafumi, and... Mamoru? Possibly foreshadowing to the fact that Reiji already knew the kid wasn't his.
That Man Is Dead: Beginning with the end of Dramatic Precious, he gives up his identity as Omi and with it his remaining innocence, in order to take up his father's former position in Kritiker as Persia. The other members of Weiss still call him "Omi," but he lays that identity to rest for good after rejoining them for one more mission in Gluhen, and identifies himself as Mamoru Takatori thereafter.
Tykebomb: Persia took him in as a child following his kidnapping, and raised him to be an assassin.
Cartwright Curse: Yoji has the worst luck with women of anyone in Weiss, with at least seven women that we know of dying after he gets involved with them. This is partly the result of his role as a Honey Trap for Kritiker, but as Dramatic Precious proves, even nameless one-night-stands aren't safe.
Chivalrous Pervert: Deconstructed. He's got the personality type in full force - and because of that, his Cartwright Curse and his role as a Honey Trap take a heavy toll on him emotionally, leading to a protracted breakdown that starts in Dramatic Precious and reaches its culmination in a near-Face-Heel Turn in Gluhen.
Walking Shirtless Scene: Mainly Gluhen, where his mission clothes lack a shirt. He occasionally forgets to do up the top three buttons on his shirt, though.
What the Hell, Hero?: He calls Ken out for thinking he can just run off with Yuriko: "How many people have you killed? And you can hold her with those arms?"
Would Not Hit a Girl: per Word of God. He actually kills three women over the course of the series (Neu, Schelle, and Tsuji) but only after each of them beats the crap out of him and leaves him with no alternative, and it emotionally destroys him every time, leading directly to the very bad place he's in during Gluhen.
Deliberate Injury Gambit: The former Trope Namer, back when it was named I Have Two Kidneys. In order to take out Godmode Clone Toudou at the end of Gluhen, Ken grabs him from behind and covers his mouth, and calls for Aya to run them both through.
Deuteragonist: Side B, arguably Dramatic Precious. He's even the Protagonist of Verbrechen and Strafe.
Establishing Character Moment: in Assassin and White Shaman, when his reaction to "Remember this guy who attacked you yesterday? He's your new teammate!" is to punch Aya in the face, and then say "It's nice to meet you." Youji says this was how Ken "greeted" him, too.
Theme Naming: Most Kritiker agents are known by their code names. Weiss and their handlers are named for cat breeds, the Aoba Center agents are named for flowers, and Crashers and their handler are named for chess pieces.
What the Hell, Hero?: You know you've screwed up when it's the villain of the piece calling you out. More exactly: "You tell ME I use my sons to my advantage?! Look at the way you treat your four subordinates, you hypocrite! Specially the little guy whom you thought he was my kid... and who happens to be YOUR illegitimate son! Bye bye!"
Manx (Hanae Kitada)
Almost Dead Guy: In Dramatic Precious, after being fatally injured by La Mort, she holds on to life long enough to inform Weiss that Birman has been taken hostage and to give them their mission.
Driven to Suicide: After she is tortured by Ayame in Dramatic Precious, when Weiss insist on trying to rescue her rather than killing her as per their orders, she shoots herself in the head rather than allow her injuries to slow down their escape.
Wife Husbandry: To Sano and Uno, two girls that he bought as children, enslaved and trained to be deadly bodyguards, used as sex toys, and was planning to have Mamoru marry one of them to ensure heirs.
Chess Motifs - The members of Crashers are code-named for chess pieces.
Vitriolic Best Buds: With Aya, mutually. Best example is when Aya asks how things are going, Knight says he's being weird, and Aya snarks back that he's not asking about Knight, he's asking about Knight's sister.
What the Hell, Hero?: In the last episode of Gluhen he calls out Persia IV for apparently sacrificing Weiss.
Hearing Voices: He complains that it gets hard to tell which thoughts are his.
I Was Just Passing Through: He saves Ken and Omi from Geisel in Gluhen but informs them that he plans to kill them next. Admittedly in Schuldig's case, unlike Nagi's below, this is probably more or less true.
Faith Heel Turn: "Jei" was a devout Catholic until he learned that he was adopted and that his biological mother was the nun who was his teacher. As an adult he claims that his desire is to kill God, and spends his spare time torturing priests to death.
Karma Houdini: Again, it bears repeating. Farfarello is singled out as one of Weiss' targets, kills Ouka, almost kills Tot and arguably gets the happiest ending in the series.
Criminal Amnesiac: Guidebooks reveal that Neu is really an amnesiac Asuka, Youji's old partner/girlfriend. She was captured by Liott, drugged, broken down, and forced into prostitution until being sold as a guinea pig to Masafumi Takatori. The amnesia was probably a relief.
Broken Bird: See above description, although Neu presumably doesn't remember this.
What Happened to the Mouse?: Okay. Tot comes back from the dead, presumably from Nagi's powers. Then she gets a five-second cameo in the final episode of Kapitel. So, um, what happened to her relationship with Nagi...?
President Evil: Well, Prime Minister Evil. Although the positions are not the same thing, he still manages to fit the trope perfectly for the short time he holds the position before Aya kills him.
You Can Keep Him: When his young son Mamoru was kidnapped, he refused to pay the ransom and abandoned the boy to his kidnappers out of spite over the fact that Mamoru was actually the product of his wife's affair with his brother Shuichi, aka Persia.
Flower Motifs: Aside from the Theme Naming: Shion's initial appearances involve ikebana, traditional Japanese flower arranging; he also goes to the flower shop where Aya's sister works and buys expensive orchids (a play on Aya's given name). Omi's last message to his teammates, notifying them that he's killed Rindou, reads "The gentian ["rindou"] has been plucked."
Four Is Death: Notable aversion; after the many repetitions of the trope in previous installments of the series, Kryptonbrand is a three-man team prior to the additions of Ken, Aya, and Yuki, and a six-man team thereafter. This may be why Kryptonbrand is ever so slightly less screwed up than Weiss.
Multinational Team: Ken & Aya = Japanese; Yuki = Japanese-American; Michel = Irish, raised in England; Chloe = born in Romania; Free = born in Liechtenstein.
But Not Too Foreign: Yuki, the first of his new teammates that Aya meets after leaving Japan, is Japanese-American.
Kid with the Leash: Of sorts. In order to allow Yuki to keep the promise he made to Alison never to kill, Aya kills for him.
Stoic Spectacles: A head injury he suffers during the fighting between Orphan and Blue Eyes causes him to need glasses; coincidentally, Akagawa's betrayal and Alison's death during the same arc leaves him with an unusually stoic attitude for his age.
Brother-Sister Incest: Played with. She's believed to be Omi's half sister due to him being Mamoru, the youngest son of Reiji Takatori, who is also Ouka's dad. But wait, there's more! Since Mamoru was actually the son of Reiji's wife Kikuno and Reiji's brother, they're actually Kissing Cousins instead. Or were, considering that Ouka ends up kicking it. Oh wow, what a mess.
Ojou: Played with a little. Her classmates consider her rich and snobby, but she's much louder and more forceful than the typical Ojou. Turns out she's a rich politician's illegitimate daughter and her forcefulness is a result of feeling neglected by him when she was younger.
Wax Museum Morgue: So according to "Tearless Dolls"... after her death, Ouka's lifeless body was pretty much turned into a mannequin and put in display in one of these? By others of the grieving, apparently maddened Reiji? What The HELL?!
Expository Hairstyle Change / Important Haircut: She grows her hair long in the vague hope that it will appeal to Aya by increasing her resemblance to his sister. At the closing of Kapitel, however, she has it cut short again.
Rescue Romance: She falls for Aya at least in part because he keeps rescuing her, although he doesn't return her feelings.
Twin Switch: Takes advantage of her resemblance to Aya's sister by stashing Aya-chan in a closet and taking her place when she's in danger. Schuldig is not amused when he finds out they've been screwed, but it doesn't stop him from using her to do it again to the Esszet elders.
Better to Die than Be Killed: Subverted. He's about to kill Kaori and then kill himself, before he changes his mind and suicide charges the Rats so she can escape. He gets shot up and she gets captured.
Break the Cutie: She thinks her parents died in an accident, then she's chased by strange men, then it turns out her parents are still alive and had used her as a guinea pig for a strange drug, then her parents are killed in front of her by Side B, and then she goes to live with her parents' murderers and endure more experiments. She doesn't mind that last one too much as KB promised they want to discover the curable properties of the Human Interleukin-3 in her blood.