Anime/Manga
Most of what I'm recommending here I either know of or personally consumed in anime format -- manga probably exists for all or most of it, but anime tends to be more accessible and can feel like the 'realized vision' of a successful manga, so I'm lumping them in.


1. Case Closed / Detective Conan (Detective, Mystery)
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This is an old classic manga with an anime adaptation. The premise is about a high school-age detective who assists the police on investigations -- pretty straightforward, until an evil criminal organization ends up poisoning him. Except instead of killing him, the poison... turns him into a young child. He's still super smart, though, so he solves mysteries better than anyone else -- but he has trouble being taken seriously, being a kid and all. He figures it out eventually, maybe. I haven't watched this one, but it's kind of a classic and the first one that comes to mind on the subject of literally having "detective" right there in the name.


2. Lupin the Third (Crime, "Gentleman thief")
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You might have heard of Arsene Lupin, an early and notable example of the "gentleman thief" character. His grandson -- Lupin the Third, as it were -- stars in this wacky adventure following a bit of a wacky and charismatic master thief. This is another classic anime even for those that aren't fans of the genre, and is known for its style and charm. Again, not one that I've watched, but the name commands respect.


3. Baccano! (Crime, Fantasy)
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Okay, so I actually don't know a whole lot about this one, but there's some legit fantasy shit, like alchemy and demons and stuff. But also, there's the mafia, so that's cool? Again, I don't know the most, but I think you follow a lot of different individual plotlines that ultimately tangle up in some way, like some kind of Pulp Fiction, but with a lot more magic, and a little more gangsters. It comes highly recommended from some friends and it's again, a well-respected anime.


4. Cowboy Bebop (Crime, Sci-Fi)
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Cowboy Bebop is set in a future where shit is so crazy that instead of dollars, the main form of currency is double dollars. Follow a gang of lovable, quirky outlaws including an ex-cop with a cybernetic arm, a child hacker with an intelligent corgi dog pet, and just about the most sarcastic, casual badass you'll ever find in the form of its main protagonist, Spike Spiegel. Cowboy Bebop is usually regarded as one of the best anime of all time, and deserves to be mentioned in any list because of its sense of style and fantastic execution. Watch this clip to get a taste. https://youtu.be/utLWiscq8d4


5. Puella Magi Madoka Magica (Magical Girl, Gay)
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Most everyone knows of Sailor Moon and other anime within the magical girl genre -- with their cheesy, drawn out transformations, villain-of-the-week plotlines, and usually childish morals like "friendship wins in the end!" Puella Magi Madoka Magica, often shorted to PMMM or Madoka Magica, plays with the genre in a way that captures the attention of an adult audience. Madoka is a fan favorite, earning unabashed praise from many who watch it. It benefits from being short and sweet, and deliberately avoids queerbaiting.


6. Death Note (Mystery, Detective, Supernatural)
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A very well-known series, though not everyone agrees on exactly how good it is. The basic concept follows the existence of a notebook that belongs to a grim reaper, who kills anyone whose name is written in it. The series initially follows a teenage genius who finds the notebook, and uses its power to make the world a better place through his own eyes -- though ultimately you also follow the police and other investigators as they try to solve the mysterious deaths. A bit of a drama series where only the viewer knows the true killer, and follows the investigations of others as they draw their own conclusions. A game of cat and mouse where the viewer observes both sides. Controversial between some, but it's part of one generation's weeaboo starter pack because of its pedigree -- it's a good anime.


7. Zankyou no Terror / Terror in Resonance (Crime, Detective, Drama)
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Two genius teenage boys execute a number of terror attacks -- but of course, can't get far without having to circumvent police interference. Watch the detectives try to puzzle through the terrorist plots, the terrorists try to execute their next big plan, and questions constantly arise about the motivations of just about everyone. The concept may sound like it's meant to bait a reaction, but the anime stands on its merits -- well-executed animation, a beautiful soundtrack, and lots and lots of emotions.



Visual Novels

1. Danganronpa: Trigger Happy Havoc (MATURE CONTENT, Mystery, Killing Game)
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Danganronpa focuses upon a high school that invites only the most gifted students in all of Japan to attend -- picking one student apiece with amazing talents in a particular field, referred to as their "Super High School Level" (or "Ultimate") talent. Ranging from the practical "Ultimate Swimmer" and "Ultimate Writer" types, to the less conventional "Ultimate Fortune Teller" or "Ultimate Heir", to the silly -- an "Ultimate Lucky Student" whose attendance is randomly determined by a lottery of all high school students in Japan, these talents unite the cast of characters. The situation, however, pits them against each other -- in a strange twist on the opening ceremony, a whacked-out school mascot announces that if a student wants to leave the now-barricaded doors, they need to kill another student -- and get away with it. Playing a run-of-the-mill student who was "lucky" enough to get invited, you're thrust into the middle of a big murder party -- and to get through it, you need to gather evidence and suss out the killer in a plot that teeters between kooky and grim. This game is brutal -- if you do take a look at this, expect to find blood, and plenty of it. But if you like what you see, you'll find that there are some extra games in the series that will keep you coming back.


2. 9 Hours, 9 Persons, 9 Doors (MATURE CONTENT, Mystery, Killing Game)
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Another popular mystery in the 'killing game' genre, though this one has some different nuances to it. Kidnapped by a mysterious masked man, the protagonist and eight other survivors find themselves locked in -- locked into a sinking ship that looks an awful lot like the Titanic. Their captor begins to name off some grim announcements -- namely, that on top of the imminent threat of the rising waters, the characters are threatened with death-by-explosion should they not play by the rules. An eccentric cast of characters try to navigate the stressful scenario and the danger they encounter along the way, and solve the mystery on multiple levels: "Who brought us here? How and why did they do it? Why us, and not anybody else?" The game has multiple endings and encourages playing through more than one to unravel the mystery at all sides. Be warned of the mature content, though -- did I mention that people MIGHT explode?


3. Ace Attorney Series (Legal/Detective, Crime, Mystery)
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Known more generally as the "Phoenix Wright" games, series fans tend to call the series as a whole "Ace Attorney" after later games in the series. Follow a plucky -- but goofy -- defense attorney as he tries to defend the unluckiest defendants you can possibly imagine. Known for wacky, animated characters, charming dialogue, and some genuinely interesting mystery storylines, Ace Attorney games have been going strong for six main installments and two spinoffs. Originally released on the DS, you can also find the original trilogy as mobile ports these days. Despite dealing with murder, nothing ever gets too graphic, generally speaking, so it actually is a lot more accessible than the first two on the list.


4. Professor Layton Series (Mystery, Detective, Fantasy)
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Professor Layton may not be a proper detective, but he deduces like the best of them in this series. With six main-line games and additional spinoffs abound, (including a crossover with the aforementioned Phoenix Wright) Layton is a professor of archaeology well-known for his love for puzzles and riddles. In a world obsessed with puzzles, this is a good trait to have -- as you can hardly tap on a character without being asked to solve the most recent riddle they've come up with. Each game boasts at least 100+ brain teasers and puzzles, and you'll genuinely feel like a genius when you solve some of the stuff they've come up with. The plotlines tend to be a fantastic in both senses of the word -- the series doesn't shy away from the occasional spot of "magic," but the mysteries are genuinely a joy to watch unravel before you, as well. Easy to recommend to wide audiences.