I'm very late to the party but someone pointed me to this thread so I am sharing my story. It's been posted before on reddit.
This stuff happened in an apartment I lived in the Lakeview neighborhood of Chicago, IL. I moved into this apartment, a typical Chicago four plus one, in Sept. 2003, and my husband (then-boyfriend) moved in Oct. 2003. We had 2 cats--a light orange tabby and a mostly-white calico (still have them, too!)
I had a few experiences at this apartment but what I'm sharing here is the first experience (and most terrifying). I have had other paranormal experiences since moving out of this apartment but none of them can hold a candle to this one. It took me 8 years to come to terms with this experience. I am a very logical person and for the longest time I was at a loss to explain this. But there's one thing I know for sure--it absolutely happened.
In late summer/early fall 2004, I went to bed one night but as usual could not fall asleep quickly. Our cats normally went to bed with me but they didn't on this night, so I sat up in bed, hoping I would see them and could call them to me. It was dark but not pitch dark because the apartment's windows let in faint light. When I sat up, I focused my eyes on the hallway to see if I could spot the cats playing/running around. But as soon as I focused my eyes on the hallway, I realized there was a very dark black (the blackest black you can think of--blacker than black, even, like velveteen tar) mass just past where the very brief hallway ended and the dining area started. It was around 7 feet high, and had a rough head and shoulder/torso shape but the rest of it kind of faded off.
I wasn't alarmed at first--if anything I leaned forward to try to get a better look, because I absolutely couldn't believe my eyes. I was baffled! But when I leaned forward, the thing seemed to turn and look at me, and when it did, I saw two red eyes in the "head". I did not see any other features and I don't remember if the eyes were glowing or just plain red but they were indeed red (and this is the biggest reason it took me so long to come to terms with this experience--red eyes are supposed to be of horror movies and scary stories, not reality).
When the thing looked at me, my amazement/confusion was quickly replaced by fear. And then it swooped through the bedroom doorway and towards me. I did the only damn thing I could think of, and that was duck under the covers like a kid hiding from the boogeyman.
I was scared shitless...I have been in some scary situations in my life but that particular fear was primal and almost unearthly. After several moments I began to run out of air beneath the covers so I decided to elbow my sleeping husband in the ribs hard enough to irritate him and make him wake up/sit up/roll over/DO SOMETHING. It worked and when he didn't react strangely I figured the thing was gone....and it was.
(I wasn't able to get up to use the restroom in the middle of the night for weeks after this...I also made it a point to NOT look at the doorway if I did happen to wake up in the night.)
I--and later my husband--saw the shadow again but it never appeared remotely as threatening.