ITT: I post my favorite fanfics, why I like them
The Sun Soul
https://www.fanfiction.net/s/5367085/1/The_Sun_SoulPokémon made grimdark. Pokemon are deadly, Team Rocket are competent criminals and Ash lost Pallet Town, and his mother, to a Gyarados attack. Well worth a read.
The Game of the Gods
https://www.fanfiction.net/s/1518794/1/The_Game_of_the_GodsDo you hate Mary Sues? Of course you do. This LoTR parody fanfic examines many different types of Mary Sues, takes away their abilities to warp reality and gleefully watches as they self destruct.
The Original Naked Quidditch Match (SFW)
https://www.fanfiction.net/s/3689325/1/The_Original_Naked_Quidditch_MatchThe Weasley Twins have lost a magical bet and the Gryffindor team has to play their next match naked. It's done in a different manner than most fanfics, presenting the storyline through a series of e-mails (or m-mails as they're called). Not much of anything sexual but quite amusing.
Harry Potter and the Methods of Rationality
https://www.fanfiction.net/s/5782108/1/Harry_Potter_and_the_Methods_of_RationalityPetunia married a biochemist, and Harry grew up reading science and science fiction. Then came the Hogwarts letter, and a world of intriguing new possibilities to exploit. And new friends, like Hermione Granger, and Professor McGonagall, and Professor Quirrell.
(summary ripped from fanfiction.net, I'm having a hard time summarizing this one)
Harry Potter and the Nightmare of Futures Past
https://www.fanfiction.net/s/2636963/1/Harry-Potter-and-the-Nightmares-of-Futures-PastHarry won the war. Literally everyone else is dead. Filled with grief, he kills himself to send his soul back through time to his 11th birthday in an attempt to do it all again and do it right. An excellent story that, sadly, seems to have been abandoned.
Watermelon Waterfall
https://www.fanfiction.net/s/7031899/1/Watermelon_WaterfallAll seems lost. The Mythic Dawn stands at the gate of Cloud Ruler Temple. All the Blades have left are five thousand scrolls of Absorb Mercantile and a watermelon…
=40k fics=HS40k (Highschool 40k)
http://1d4chan.org/wiki/HS40KScout, the younger brother of the all star jock Ultramarine, tries to woo Cultist-chan. In the grim darkness of the far future, being a teenager sure is complicated. A cute fic.
The Shape of the Nightmare to Come: Warhammer 50k
http://1d4chan.org/wiki/Story:The_Shape_Of_The_Nightmare_To_Come_50k10,000 years have passed since the Golden Throne has failed. Abbadon has taken Cadia and a good chunk of the Galaxy, the Orks and Tyranids have fused into the unstoppable New Devourer, the Emperor has become a Chaos God and the Necrons are awaking in greater numbers with the Void Dragon joining the show. The galaxy has gotten a whole lot worse.
Hangover Mechanicus
http://1d4chan.org/wiki/Hangover_MechanicusHangover Mechanicus was inspired by the OP of a thread that states he was at a cosplay convention dressed up as a tech-priest and he met a sexy Sister of Battle, eventually they got drunk and fucked, and he got one of his steel/machine tentacles stuck in the Sororitas costume when he woke up from his hangover. This is the resulting story based off of it.
Looted Emperor
http://1d4chan.org/wiki/Looted_EmperorThe Orks have looted the Emprah and are a part of the Imperium now.
Tinyhammer
http://1d4chan.org/wiki/Tiny_HammerA collection of stories about various factions from 40k appearing on earth…the size of miniatures. Space Marines are an inch tall, monoliths come up to your ankle, etc.
Fallen from Grace
http://1d4chan.org/wiki/Fallen_from_GraceA Dark Eldar who isn't completely insane lands on a backwater planet of the Imperium where she is mistaken by the human farmer as an angel. Adorable.
False Immortality
http://1d4chan.org/wiki/False_ImmortalityA story about a ancient Necron Immortal pondering his (un)life as he stands guard over his lord and master.
Feral World Religion
http://1d4chan.org/wiki/Feral_World_ReligionA hilarious piece of writefaggotry posted by an anon about an isolated feral world and their interesting spin on the Imperial Cult.
Fuckin' Adeptus Mechanicus
http://1d4chan.org/wiki/Fuckin%27_Adeptus_MechanicusA young man invents a revolutionary new form of rake and is noticed by the AdMech.
Half Life 40k
http://1d4chan.org/wiki/Half_Life_40kGordon Freeman bunnyhopping around 40k laying waste to the enemies of man. What more needs to be said?
The Game
http://1d4chan.org/wiki/The_Game_%28Tzeentch%29Who's a match for the Chaos God of plots? Creed, that's who.