As an intro...In my experience there just isn't a whole lot of quality in Glee fanfiction. IDK I could be totally wrong. It's just that the fandom is so huge at the moment good!fic tends to get completely lost in a sea of OCC, second hand embarassment and overly feminized gay characters. Kurtofsky specifically has a lot of dub-con/non-con that I haven't even thought about reading. That being said...
In Which A Delusion Is Lived Through- Hard R
In another world, something completely different might had happened.
Angsty non-au au. By far my favourite of the whole fandom so far.
The Kurtofsky IM Sessions NC-17
An unlikely friendship starts through a series of IMs
Alternative fic written mostly in IMs, though there is some actual writing in some of them. It is so addicting, the updates are the highlights of my day. I'd classify it as canon-based AU I think. It's sweet and funny and has some awesome original characters. (Warning: Blainebashing/Bastard!Blaine)
Karofsky begins to think that he may be a little too chubby so he does something about it, and it starts to spiral into something that he can't handle or even acknowledge, because only girls get eating disorders.
More of a Karofsky character piece but so, so angsty. :(
Melting The Ice PGish
Kurt had wanted to put that whole kiss with Karofsky behind him, but life doesn’t always give you what you want (just what you need).
Short piece of fluffy h/c.
Of Snow and Coffee and Hermes Scarves PG-13
It's getting frigid outside in the Ohio weather. Kurt forgets he doesn't have a ride home after school and is left standing in the front waiting for a miracle while thinking about things that are warm. The miracle comes in the form of Karofsky telling him to get into his car. Kurt is reluctant, but he really wants to go home so he goes for it. Until he realizes that Karofsky isn't heading towards Kurt's house, but his own...
Based on a prompt from the kinkmeme, it actually gets fairly fluffy. The formatting throws me off somewhat, but a nice piece none the less.
Of French Projects and Fooling Around R
Dave and Kurt are paired together on a school project. Dave has a little bit of trouble concentrating so Kurt suggests a solution.
Hits on my "take what you can get" angst kink. Oh, teenagers.
Ivory and Gold R - NC-17?
Prompt: I definitely see Kurt and Karofsky getting together, maybe now or maybe a few years down the road. I've always thought Karofsky was playing much dumber than he actually is and once high school ends he doesn't have to play the part anymore. But he's still Dave Karofsky. One day he and Kurt get into a huge fight. They argue and argue and Karofsky bangs the wall/cabinets/whatever with his fist. And Kurt flinches. Flinches like he used to, like underneath it all he's still just waiting for that punch he told Karofsky to give him in the locker room. Cue major angst and some super intense h/c smexing.
This started off as, and is still considered, to be the best fic of the ship. I stopped reading around part 19 and it's now on part 33. It got a bit OCC for me and I have no idea what's going on, but I'd be remiss not to mention it.
Prompt: Masturbation fic, Karofsky thinking of Kurt, preferably as worshipfully (but still very smutty) as possible. All about what he secretly thinks about Kurts skin, eyes, hair etc. when he's completely alone."
Uh. Wank porn. Yeah. :)
You can also take your pick of Filled Kurtofsky prompts from the kink meme and there's also some lurking around glee_angst_meme and glee_fluff_meme :)
Those are the ones I can think of off the top of my head. I may get back to you once I search through karofsky_hummel for fics I read and didn't book mark XD.