Reposting from BG, plus some additions
Yeah, yeah, I know - weeaboo, blah, blah, blah... I've heard it all before, usually from my gaming groups in fact. Which is why I feel totally free to rip off NPC's and plotlines wholesale to use in the campaigns I run^^ They seem to still enjoy it, despite the source, and if they think I'm a creative genius, well what they don't know won't hurt me^^
Because really, as a DM, I find I can make the NPC's much more believable and "real" if I have a personality in mind to attach to the role. Instead of spending time rolling up or thinking up different quirks for bartender #37, I can slap a quick name on it, and have a personality, appearance, quotes, the whole nine yards - and I can do it on the fly if need be. Now, of course you can do this with any TV show, books, movies, etc but I find you run a much larger risk of someone recognizing the rip-off. Nothing breaks immersion like the group being introduced to your criminal mastermind contact and a player going "oh hey, it's Nate from Leverage".
So, I thought I would put together a list of mostly lesser known works that I've found handy to steal from. For the ones I leave blank, you can fill in "Generic fantasy world with lots of characters that can be lifted and put into the plot with no change"
In no particular order:
Dark Air - Park Min-seo: This is a fun one for a group that wants to run a more magic-lite campaign, at least to start. Like a lot of Korean fantasy manhwa, it has a very RPG flavour to it to begin with, so it's not hard at all to fit it to D&D. 3 years before the story starts, magic completely disappears from the world (or almost completely...) leaving a huge power vacuum. Small mercenary groups of 3-8 people act independently in the chaos, adventuring or doing missions for the nobility. Lots of varied fighters, with bard-like "buffer" roles as the only remaining magic. Lots of good stuff here.
ID - Kim Daewoo: Another fantasy manhwa, this one is about a dimensional traveler from a Wuxia-style world that gets stuck in a traditional Western-style fantasy world. Hilarious, and with an interesting story to boot.
Berserk - Miura Kentaro: The handbook for running a morally grey/black campaign and still managing to keep some semblance of heroism. Also has (as you might guess) one of the most bad-ass Barbarian/Berserker-type characters ever. It is fairly well known though, so steal characters with caution.
Ubel Blatt - Shiono Etorouji: Another really dark manga, this one is really good to pull villains and plot from. I'm just waiting for someone to play a paladin in my group so I can launch this bad boy on him.
Paladin - Ryu Kee-Oun:
Magician - Kim Sarae: Lots of wizard-types
Dark Mage - Kim Jung Ryul:
Immortal Regis - Ga On-Bi
Sacred Blacksmith - Miura Isao: Some interesting Legacy items in this one
Rave Master - Mashima Hiro: Light-hearted and comedic, good for some real "WTF?" characters when you need some silliness
Jackals - Shinya Murata, Kim Byung Jin: Need some real psychopaths and/or some serious dark gray anti-heroes?
Shin Angyo Onshi - Youn In-Wan: This one is a bit slow to start, but after a few volumes, it gets into the real plot and there are a lot of "doing the wrong thing for the right reasons" type villains if that's something you want to explore.
One Piece - Echiro Oda: I have to add this one in, even though it's not very D&D-like, but there are so many good personalities to steal - and the background storyline can be interesting to use as well.
Anime (often based on games or light novels)
Dantalion no Shouka: I'm a huge fan of this series, ever since I picked the books up a few years back. Lots of good ideas for "magic item is wreaking havoc" adventures
Sands of Destruction
Legend of Legendary Heroes
Tears to Tiara
Seirei no Moribito
Baccano! Not D&D at all, but a huge amount of colorful, memorable characters - by the same writer as Durarara
Kaibutsu Oujo: For all you Necropolitan fans^^
Rental Magica a varied cast of magic users for those that like to change up the superficial appearance of magic
There are, of course, hundreds more, but I thought I would start small and add more as I go. Hopefully someone will find this useful =)