Alrighty, I've got a few stories, but I'll share my most memorable one, and I apologize in advance for the length :D
Back when I was a freshman in college (2008) they offered "haunted ghost tours" of some of the more historic buildings on campus. To be fair, most of the buildings were old, as the school was built in the late 1800's. The oldest building on campus was originally a hotel that had been converted into dorms for the upper-classmen and it was an all-around creepy place.
My roommate and I were both really into that spooky shit so we went, listened to the lecture from the lady conducting the tour, and then we were left to go "hunting" on our own inside this dorm. While a creepy place, it didn't really give off any odd vibes so I was sure nothing was going to happen.
Fast forward about 30 minutes into our exploration (they had given us a full hour to "hunt"), and we find ourselves in the basement. Concrete walls and floor, no paint or light fixtures, and no other students messing around. It was a complete 180 from the upstairs portion of the building. There was a single hanging light bulb that lit up a room just big enough for 2 washers and 2 dryers (maybe 8x8? There was just a little path to walk between the washers and dryers). Past that was a very narrow hallway with a door at the end. I had started to get a liiiiittle weirded out at this point but my roommate was all excited to see what the door led to so I followed along.
We open this door to find the fkn creepiest bathroom known to man. It was a 3-stall bathroom like you'd see in a school, with wall to wall mirrors across the front, with 3 sinks. Pretty average, right? Except the mirror was terribly cracked, shattered in one place where it looked as though someone threw a chair at it. Two of the sinks were busted and the third sink was altogether missing. The stall doors were hanging at odd angles, and even the tile floor was cracked and pitted.
Thankfully the fluorescent lights worked, so that was a plus. But entering the bathroom, my feelings changed dramatically. The hair on the back of my neck stood up, I began to feel anxious and legitimately scared, and I asked my roommate if we could just go. What does she do? Lock the fkn door and turn off the lights.
Yeah. I know. I wanted to punch her. Now she starts asking questions into the darkness ("Is there anyone here with us? "What's your name?" etc, etc) all the while, I'm getting more and more apprehensive, to the point where I eventually said something along the lines of needing to get the hell out of there ASAP. She turns the lights back on, unlocks the door, and we bolt out. As soon as we're out of there and back upstairs, the anxious feeling is gone. The whole encounter may have lasted 5 minutes.
Fast forward a few hours...
We're back in our room and I'm going over the recording I took with my phone when I come across the bathroom scene. As I hear my roommate's voice in the background, muffled and asking questions, this LOUD whisper comes over the speaker saying "Get Out!" as though it were right on top of the microphone. When she asks her last question, I hear the voice again, a little quieter, say "Gooo...". That was right before we bolted out of there. It was just the two of us in that bathroom, and neither of us heard ANYTHING while we were actually there.
Still creeps me the fk out thinking back on it.