Per se

NOT WRITTEN "PER SAY". PLEASE.
Often used by kids that don't know the actual meaning of it, just to sound smarter than they really are. If you use it normally though I've got zero problems with you.
Means "I want to insult someone/something, but also want to water it down enough to not get my ass beat" in most contexts.

John: "I think the new book our English teacher gave us is absolute trash."
Stacey: "I wouldn't say it's trash per se, but it is a bit boring..."
John: "Bitch please just admit it's awful."

Fanfic

Either the most disgusting or the most beautiful piece of media you'll ever read. An either small text or a book-worthy story written by a fan of any movie/show/book etc., featuring the characters from said movie/show/book etc. often doing unspeakably filthy things or getting traumatized even more than they already are.
Wherever you're reading, be it Ao3, or...God forbid...Wattpad, it's the most important thing to READ THE TAGS!
Trust me, you don't want to start reading and come across "Dead Dove: Do Not Eat" material three chapters in.

Dave: "Hey look at this new fanfic I found!"
Jim: "Dude...its tags are literally 'M/M/M/M/F-fivesome', 'bees' and 'metaphorical splinters because of THAT WOOD'"
Jim: "...I'll check it out."