These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Better on DVD: The monthly installments come out looking essentially like sketches; spit, polish, background art, and easier-to-make-out gunfights are included in the tankoubon releases.
Complete Monster: Angelika Einstürzen is a Mad Scientist whose specialty is human experimentation, and she starts on her test subjects when they're young children. Chronologically, the first thing we see her do is tell Heine that if he took part in the extremely dangerous Master Kerberos Spine experiment, he'd save all of his friends from the same fate. Once it was clear that Heine had successfully bonded with the spine, she no longer needed the rest of the test group and had them go berserk and murder each other, and she forced Heine to watch. Next, she sends a large number of her old test subjects to invade the Underground City and slaughter as many people as they could before she blew her soldiers up. She didn't even do this because she had something against the people she had killed, she just wanted to get rid of her old, defective test subjects and at the same time, get the attention of the mayor, who resided on the surface, and she figured the easiest way to kill two birds with one stone was to blow her men up and take hundreds, if not thousands of innocent civilians with them. Afterwards, she sends one of her many bodies to Stray Dogs District and tells the people there that their friends and family, who had been kidnapped long ago, were among the attackers that the Stray Dogs had killed, just to see how horrified they would be. It's telling that one of the nicest things we can say about her is that she shocked Luki when the twins understandably didn't want to go back to her for more brainwashing and Mind Rape. She does all this for one of two very simple reasons: scientific research and amusement.
Fan-Preferred Couple: Heine and Naoto, although if things keep going in the direction they have been, they'll become not so much fan-preferred as they will be official.
Fridge Brilliance: The weapons that Heine (Mauser C96 and Luger) and Giovanni (Walther P38) actually reflects their characters and their relationship with each other to a startling degree. The C96 and Luger are verycool guns, but they were both quite impractical: the C96 was big and heavy for a handgun, and it's vicious recoil coupled with a ridiculous rate of fire when set to automatic, made it difficult to handle. The Luger is to this day considered one of the most elegant pistols of all time, and even by today's standards, its accuracy is nothing to scoff at, but it was hardly reliable: it required extremely high grade ammunition and even a little bit of dirt would cause it to jam. The P38, on the other hand, is the Boring but Practical counterpart to these two guns: not nearly as distinctive as the other two guns, but reliable enough that a barely-modified variant was still being used by the Bundeswehr into the 2000s. Like his guns, Heine is showy and impressive, and he does his own thing the way he wants to, but he's also extremely unstable and even he has trouble controlling himself at times. Conversely, Giovanni is more boring: he wears a suit instead of Heine's Impossibly Cool Clothes, he's calm and collected while Heine is Ax-Crazy, and he's very easy for his handlers to control. Furthermore, the Walther P38 replaced the Luger and did its job much more reliably, just like Giovanni replaced Heine in the organization after Heine escaped.
Funny Moments: Usually whenever Badou, Dominico and/or Marcel show up.
Heine and Badou definitely have a screwball couple dynamic. Particularly, Heine has a fear of women because of abuse in the past. When Naoto throws a sudden, suspicious (and hilarious) look after hearing this for the first time (we were all thinking it), Badou goes on record saying: "I'll say this only once: it's not like that." (Riiight, Badou. That totally did not induce a reaction opposite to what you expected from the Yaoi Fangirls... At all.) To be fair to them, they're both obviously straight and even have separate Love Interests, but when has that ever stopped shippers.
Giovanni has an unhealthy obsession with Heine that can get pretty suggestive at times.
Jerkass Woobie: Despite his several Pet the Dog moments, Heine's still a huge prick, but even as you feel the need to call him out on his behavior, you can't help but feel sorry for him because of all the shit he's been through.
As of recent chapters, Giovanni as well, especially since, for all his gripes, Heine managed to escape Einstürzen. Giovanni, on the other hand, never did.