I will take anything except romance(this discards any novel from twilight and novels similiar to it.). I will prefer is the fanfic main genre is action or comedy.
God of Soul System - the MC gets reincarnated into One Piece world, later on travels to Naruto and Bleach world. I have only read the whole OP and half of Naruto world plot. I like how the MC changes from an ordinary guy into a fighter who don't mind killing and fighting for what he wants. Also, the story as far as I have read, doesn't have main points on the characters we know from OP/Naruto anime/manga. We do get to see Strawhats pirates here and there, but only for a short while and in Naruto world, as far as I have read, we get to know of a couple of old timers and Kage guys.
What is your favorite series? Maybe I can recommend something if I know what series you like. For my personal recommendation: Code Geass: The March of Time. Lelouch return back in time to change the past. Updated monthly. The Beacon Civil War. RWBY fanfic about Beacon in civil war. Keeping the war theme as hilarious as possible. Highly recommend it if you like comedy. Fate Revelation Online. A crossover between Sword Art Online and Fate Stay Night. If you wonder how magic system work in Aincrad then I will highly recommend this series. The Vasto of White. Bleach and Fate Stay Night crossover. Shiro is reincarnated as Vasto Lorde with an UBW ability. What will happen if you put an ability to copy anything resembling sword to a world where most inhabitants are sword user? Very obvious, right?
The only "confirmed" one is Spoiler: Spoiler Boa Hancock The MC have followers, but the only romance so far is only her.
God Slaying Blade Works Fate/Stay Night and Campione crossover. Heavens Feel Shirou and Ilya pulled into Campione World by Grail and became the Eighth Campione.