A lot of creepypastas genuinely freak me out.  That's why I enjoy them so much.  I have a list of the ones I like best on my profile.  Many (but not all) of those are stories I find genuinely terrifying.  (The others are ones I like based on literary merit.)

Less of a freakout and more of a morbid realization of just how wrong the things in the plot are going, yeah.

I recently read one that skeeved me out. Ingrown I'm sure I'll be thinking about it the next time I trim my nails, which I maintain meticulously. I want to make that clear.

A few kind of have, but I don't even remember what they were about. One that I do remember that made me flinch every time I heard a noise outside for a few days was about a creepy guy knocking on people's windows at night or something like that, but I don't remember what it was called or any details or anything.

The reason it had that effect on me was that my apartment building's balconies were being renovated, so there were platforms outside allowing the workers to walk up to the third floor (where I live), meaning that technically anyone could've walked up. Actually, they could've even come inside because it was a particularly hot summer so I kept the balcony door open. Just after I'd read the story, a squirrel ran across the platform, which really freaked me out; I was alone because my mum was on a holiday half across the country (which is still relatively close, but well). I called her in the middle of the night and was like "SOMEONE'S COMING TO KILL ME, oh nevermind it was just a squirrel... sorry". She was pretty annoyed, haha.

One that have me the chills, was actually a very short one, I can't remember the name of it and I won't give the twist away in case anyone hasn't read it is about an old Japanese fellow who has a rather unusual ability; being able to tell the last thing that someone has eaten. 

The horror of the story is subtle but very clever.

Ah, yes, The Man Behind the Train Station. It took me a while to figure that one out, but once you figure it out it’s spooky.

Edit: Nope, got the crappy ripoff version on accident. The original is Ability.

Ability, yes that's it. The name of the story was on the tip of my tongue but couldnt for the life of Me remember it.

Russian Sleep Experiment. There, I said it.

Dude, RSE freaked the shit out of me when I first read it.