I looking for something similar to What Would Slytherin Harry Do and Knowledge is Power. Fanfics where Harry uses his brain.

 

On the Way to Greatness. Try that

 

There is Renegade Cause by Silens Cursor and This by scaryisntit, another DLP author.

 

You also might like Harry Potter and the Natural 20, Harry Dursley and The Chronicles of the King and of course, HPMOR.
Harry Potter and the Boy who lived - you probably know it, it's here on DLP, but unfortunately it looks as if it won't be continued.

 

This is a very open-ended request. Most Harry-centric stories in the DLP Library would meet the OP's desideratum.

One that's not in the Library, but that I am following (and enjoying) nevertheless is Kwan Li's Hogwarts Battle School. The story is a HP/Ender's Game fusion (though not as objectionable as the latter).

 

Check out Methods of Rationality by less wrong trololol~

 

The OP did profess a love of SerpentSannin/Oblong/MrJoe/Fettucini/Schizophrenic/Self-Deletion-Fetishist/PretentiousDick's KiP, so perhaps not a troll?

 

It's different to the fics mentioned in the original posts in that it's not starting in 1st year but I have not heard this fic mentioned in quite some time - I'm sure that lots of people here are not even aware of it:
Secrets

Warning: It's slash: HP/DM :/
BUT: it does not contain most of the characteristics all these awful slash-fics have - no tattoos, focus on clothes or whatnot.

Instead, I would describe it as driven!Harry

Dumbledore is dead (starting after 6th year) and Harry suddenly has so many responsibilities - he has to grow up. No super!Harry but realistic leadership etc pp.
Normally I really would not recommend slash stuff but this story is really good - I'm just reading it for the 2nd time

 

I would like to mention kmfrank's story, Harry Potter and the Unlocked Knowledge which is currently in the WbA and is 15 chapters and 168,125 words. Harry does use his brain, which has an on-going commentary with the horcrux he's absorbed as of his possession during the Department of Mysteries battle. 'Tom' is only known to Harry, and while it sticks quite a bit to canon, it's original enough and the writing good enough for me to recommend you read it. I'm actually going back through it now, and it's held up fairly well over the years (and now kmfrank's updating again... score!).

Another story I'd rec is Harry Potter and the Death Eaters of Hogwarts by Mentally Impaired, which is a pretty fun read. I think the author is editing it and reposting it as a different story, and there's already a written sequel as well.