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.
Fridge Brilliance: In Bride, Razor Eddie and Dead Boy fight a giant black centipede that's actually Rogue the immortal. Eddie cuts off several of its legs in the fight. A while later, Harry Fabulous turns up at John's stag party, offering a variety of drugs and other exotic delights... including black centipede meat! Might even be a call back to Angels, in which Eddie mentions having sold off the remains of another bunch of his kills.
Fridge Logic: In Unnatural Inquirer, John's having killed all the Elite Mook minions of a gang boss is said, both by John himself and by the Big Bad, to lend greater credibility to the idea that the Afterlife Recording is genuine. Given that John wipes the floor with Cosmic Horrors on a regular basis, and cultivates a reputation for committing mayhem on anyone who so much as snickers at his trench coat, why would this incident be seen as proof of anything, rather than written off as yet another case of dumb thugs pissing him off?
Magnificent Bastard: Walker. His Gambit Roulette in The Good, the Bad, and the Uncanny. He sets things up so that no matter what happens, John is effectively forced to take Walker's place as the Voice of Authority in the Nightside.
Completely subverted with the Merlin of Sinister Albion. Even had he not had a certain sword, John could have called up any number of beings to take him out
"Yes, but... he's Merlin!" said Alex. "Alive and in his prime, after fifteen hundred years of practicing his craft! With all the power of the anti-Christ! He could probably pull the moon down out of the sky and crash it into the Nightside for laughs! And I'm not sure there's anyone in the Nightside who could stop him!"
"Do I need to get you a paper bag to breathe into?" I said. "Of course there are people here who could stop him! Off the top of my head, there's the Lord of Thorns. And Hadleigh Oblivion, the Detective Inspectre. And Jessica Sorrow, the Unbeliever."