Warning: Here there be spoilers. Proceed with caution.
The street junkie V passes by in the Street Kid prologue mutters "the cybernetic god will devour his children!", which comes to pass in most endings.
In the "Devil" ending, Saburo's digitized psyche devours Yorinobu's as he takes over his son's body.
In the endings where you let Alt run loose in the Mikoshi, she absorbs the engrams created by the Soulkiller she pioneered.
Each of the prologues Book Ends one of the epilogues:
Street Kid starts with V hanging out in El Coyote Cojo before talking to a shady fixer and going on a job he gives them. The "Sun" and "(Don't Fear) The Reaper" endings see V hanging out in the Afterlife before talking to a shady fixer and going on a job he gives them.
Corpo sees V work with a higher-ranking Arasaka official only to get screwed over by him and tossed out. The "Devil" ending sees V working with high-ranking Arasaka officials only to get digitized into Mikoshi or sent back to Earth. Additionally, during the prologue, Jackie refers to Corpo V working with Arasaka as "Un pacto con el Diablo" ("A deal with the Devil"). Not only does the Arasaka ending involve making a deal with them, but the ending itself corresponds to the Devil tarot.
Nomad has V arrive in Night City on a job to smuggle a lizard owned by Arasaka into it. The "Star" ending has them leave Night City while smuggling the Basilisk (the namesake of which is a mythical reptile-like creature and a species of lizard) and a huge load of spoils stolen from Arasaka out of it. At the same time V in the beginning will take off their Bakker patch, which represents the Nomad family they left behind after it fractured and decides to join up with a larger clan. While during the "Star" ending, V will obtain a jacket which represents them becoming apart of the Aldecaldos, one of the larger families in California.
The six-month timeskip opens with Jackie bumping into a man wearing a Samurai T-shirt; the band's frontman becomes a major character in Act 2.
When riding down the elevator to meet Jackie at the start of Act 1, a news broadcast starts playing, talking about an Arasaka-sponsored parade, with Hanako as the guest of honor, set to come through Night City. In Act 2, this very parade, and Hanako's presence in it, becomes the focus of Takemura's questline.
Speaking with Jackie by the megabuilding entrance, V has the option to say that fixers "catch a client, find the cheapest gonk to do the job, then drop the corpse at a landfill". This is precisely what Dex does, up to and including dropping V's body in the municipal landfill.
During their introduction, Dexter tells V that when he started prodding around to find info on Evelyn Parker, "some brothers from Pacifica" told him to drop it or else. The Pacifica-based Voodoo Boyz were at this point Evelyn's employers for the recon mission about the Relic.
In the first braindance, a small-time thief robs a convenience store, only to be shot dead by another thief who instructed him on the job. Swap a convenience store for a hotel and this is V and Dex after Konpeki Plaza.
After the second braindance, Judy says that looking at the heist crew, all she sees are "walking, talking corpses," and indeed, apart from her, everyone involved in the Relic theft dies, sooner or later:
T-Bug gets brain-fried when Arasaka netrunners catch her in the subnet.
Jackie bleeds out in Delamain's back seat after being shot by Arasaka security when everything goes straight to hell.
V gets shot in the head by Dex, and though they get better thanks to the Relic, pretty much every ending implies that they die, more or less explicitly.
Dex gets shot in the head by Takemura, with no get-out-of-death-free card to rescue him.
Evelyn commits suicide after being brain-nuked by the Voodoo Boyz, raped by Woodman and put through absolute hell at the hands of the Death's Head Scavs.
Delamain can suffer a Death of Personality, depending on your choice at the end of his questline.
If you wander around the Afterlife before sitting down, you can find Panam and Nash discussing their latest job - likely the same one that will end with Nash taking the cargo and the car, both the focus of Panam's introductory quest.
When Jackie makes his order at Afterlife's bar, Claire recognizes it as a Johnny Silverhand special, and says "Johnny Silverhand, coming right up!" He is introduced in the quest immediately after the current one.
Right after Claire explains to V the Afterlife tradition of naming drinks after fallen legends, Jackie tells her the recipe for his own drink. As expected, he doesn't survive the heist.
Should V ask what perks are included as part of Delamain's premium package on their ride to the Arasaka heist, Delamain will list off its health care coverage, including the disposal of the client's remains should they die in the vehicle, something which unnerves Jackie. Jackie ultimately winds up dying of his wounds in the cab after fleeing the botched heist, with Delamain handling the disposal of his body as per V's instructions.
During the interlude, Johnny and Rogue fly to the top of Arasaka tower in a helicopter. In Rogue's version of the final mission, he (in V's body) and Rogue fly an AV to the top of the rebuilt Arasaka tower.
When V tries to take the pills to stop Johnny from acting out in their psyche, he angrily tells them to "stick some iron in your mouth and pull the trigger". In the "Reaper" ending, it's not shown how exactly V chooses to commit suicide, but a gunshot is heard.
While riding down the elevator at the start of Act 2, a news broadcast about Mayor Rhyne's death plays, which becomes the focus of I Fought The Law sidequest.
During V's, Jackie's, T-Bug's and Dexter's meeting, you can see that T-Bug's shoes have "DELTA V" written on them, with "delta" being Future Slang for "run away". It's a last warning to V before the failure that is the Konpeki Plaza heist.
"Delta" is also slang for "leave/depart". After the failed heist, V might become dearly departed in multiple ways. Also, everyone else involved leaves V, permanently.
Two songs on Kerry's laptop, "Dark Matter" and "Shivers" foreshadow the events of his Romance Sidequest, with "Dark Matter" referring to the "Off the Leash" sidequest (the club it takes place in is called "Dark Matter") while "Shivers" foreshadows the "Path of Glory" ending, which is considered the best one for players wanting to romance Kerry.
During "Holdin' On", Kerry will say that he will be pissed if Johnny spend his time when he was presumed dead with the Nomads or in the orbit. He's referencing "The Star" (the ending where V leaves with the Aldecaldos) and "The Devil" (the ending where V gets the biochip removed by Arasaka) and the fact that he will break up with V in "The Star" and will be very concerned for him in "The Devil".
Judy has an email exchange on her computer, where she talks about how she fixed up a firetruck when she was a teenager. This doesn't get explicitly referenced anywhere else in the game, so it might foreshadow "The Star" ending, where V (and Judy, if she was romanced) leave Night City with the nomad group, the Aldecaldos, who are known for their skills with cars, motorcycles and other vehicles. It's also the only ending where V and Judy stay together.
A Nomad V can mention during the Judy's arc culmination quest "Pyramid Song" that Judy and the other Laguna Bend residents had a similar experience with the corps (IE: losing their homes and livelihoods to corporate predations) that the proto-Nomads had long ago. In the Star ending, Judy will leave with a romanced female V to ride with the Aldecaldos.
After "The Rescue", V is afflicted with a mild cyberware virus that Viktor cures without much issues. It foreshadows the main plot of act two and three, where V is racing against time to cure the damage the Relic did to their brain, which shows as coughing, seizures, losing conciousness and throwing up, common signs of various illnesses.
Right before the Point of No Return that allows one to choose their ending, V can finally ask Viktor about the boxing match's he's been watching the entire game, with Viktor admitting that he knows how it ends: "[his] guy loses, every time. It's a recording", and that desptie his best attempt at finding what mistake the boxer did, the only thing he could find was "he got into the ring with a bigger opponent, which isn't really something you can call a mistake." Of course, much like the boxer himself, V was doomed the moment they attempted to get "in the big leagues", and no matter what they try, it can't save their life.
In the Streetkid lifepath, Stints says to V that "(...)it's the same for all you (Heywood) termites: born here, live here, die here". This V was born in and grew up in Heywood, returned to life in Night City after an unsuccessful venture in Atlanta, and the apartment V moves to in the "Path of Glory" epilogue, situated right next to their old flat, where they expect die due to the relic illness.
At one point in "The Ripperdoc" main quest, after visiting Viktor, you return to find Misty reading Jackie's chakra, and gives him the advice to "avoid mean reds. Anything red." Guess what color the Relic is? And the general motif of Arasaka? And Dex's outfit?
V is told early on that cyberpsychosis occurs the more a person changes out their body parts for mechanical ones. Despite this, V is never at risk of turning into a cyberpsycho no matter what they install into their body, and the player later meets Adam Smasher, a man who has become 96% machine and yet retains control over his body (even if he is extremely Ax-Crazy, though background material reveals he was off the deep end even before he got chromed). It's later revealed in the Monster Hunt sidequest that cyberpsychosis does not actually exist, and is instead a Conspiracy Theory promoted by the media, with the real "cause" being a combination of factors such as drug abuse, faulty cybernetic models, and the simple fact that the oppressive state of the world leads to a host of crippling psychological issues that are then acted out on while equipped with potentially lethal cybernetics.
Dex asks V early on if they want to die quietly, or go out in a blaze of glory, but later comments, "no blaze o' glory for me" when he shoots V to make a deal with Arasaka. The secret ending ("(Don't Fear) The Reaper") involves one such blaze of glory, though whether V "goes out" is up to the player, while V can also follow in Dex's footsteps and make a deal with Arasaka, which, while it turns out better than it did for Dex involves assisting them with bringing Yorinobu to justice rather than earning their fame with a one-person assault.
The Tarot graffiti featured in the "Fool on the Hill" quest pretty much is this for any player that completes the quest early before moving onto the later story missions, as the locations where they are found correspond to specific quests and choices that are made there during the course of the story, and each card also corresponds to events of those quests. For example, "the Fool" tarot, which is the first card in the Tarot deck and is representative of the beginning of a story or journey, is found right outside V's apartment, where they wake up after the first mission "The Rescue" and where they wake up after the conclusion of Act 1. "The World", which represents the end of said journey, is found on the terrace near Misty's store and Viktor's clinic, the place where V goes after the Point of No Return (i.e. once the ending begins) to decide how the Mikoshi raid will be done. It's also potentially the place where the journey can literally end, as it's the exact place V can commit suicide during said scene.
During one of the first times V uses the elevator to their apartment, the TV in the elevator will play a rather lengthy talk show segment with a debate about the 'Secure your Soul' program aka Soulkiller. One side of the debate celebrates it as an accurate representation of a person and a way to immortality, while the other (a preacher) says that it is blasphemous and only a fake copy, an attempt to circumvent having to grieve for people you lose. This not only foreshadows that V will soon come in contact with Secure your Soul, but also the questions they might ask (is Johnny just code, or a real person?) and also in a way the endings (since in the Devil ending, V is so desperate for life that they can go along with the program, or they can decide to rather die as a real person and reject the program)
All the intros start with V looking in a mirror. The nature of identity happens to be a Central Theme of the game.
In the Corpo path, the mirror says "TRUST NO ONE", as a general security warning. This turns out to be good advice for V in very short order.
One not for events, but for the tone of what follows, is the placement of a particular cameo. If you choose to search the bar in Konpeki Plaza during "The Heist", you can come across a BD producer named Hideyoshi Oshima, who looks exactly like his VA and is talking to a small audience about the challenges in evoking the kind of emotions films can when working in a different medium. What follows is a complex, intrigue-heavy section of gameplay involving stealth, combat, high drama, and very cinematic cutscenes, often rather long with short playable sections in between. And a bossfight with a security bot that looks like a Metal Gear.
) and a huge load of spoils stolen from Arasaka out of it. At the same time V in the beginning will take off their Bakker patch, which represents the Nomad family they left behind after it fractured and decides to join up with a larger clan. While during the "Star" ending, V will obtain a jacket which represents them becoming apart of the Aldecaldos, one of the larger families in California.