These events happened to me about 4 years ago when spent a year working at one of the largest theme parks in the UK. This place is about half an hour from where I live and while I won't name it directly I’m sure a few of you can guess where it is.
I worked there as a ride assistant, and worked on several different rides including three of the big coasters and a couple of the dark rides. For those who don’t know a dark ride is basically a ride that is completely indoors. The most common example of this is your typical ghost train. Now one particular ride is based partly inside the ruins of the family estate from which the park gets its name. The ride tells a pretty well known local story about the family that used to own the estate and a supposed curse that they were afflicted with. The ride would start with an indoor queuing area, before moving guests into a cinema which told them the story and then to a place known as the Octagon room where there would be a small effect based show. Then finally guests would unknowingly exit the ruins and board the actual ride which was a haunted swing type affair.
The actual ruins are well known for being potentially haunted with programs such as Most Haunted featuring them, and after my time on that ride I can 100% agree. One night during October, which is when the park stays open till 9 pm to allow guests to ride in the dark, I sat at the end of the queue line. A member of staff is always stationed here to ensure that there a) aren't too many people in each group and b) to greet the guests. Now usually after about 5 pm the ride became pretty deserted as most people wanted to ride the roller coasters in the dark, not walk through some very dimly lit building so my job was really easy. At the end of the queue line there was a small station with a television screen showing security camera feeds and a direct phone line to the ride operators cabin. The cameras focused on the outdoor entrance, the entire queue line and the cinema area; there weren't any blind spots either on these feeds. Now this night I was doing my usual thing, checking Facebook, playing angry birds and keeping one eye on the monitor when I spotted what I guessed was a young couple making their way up the winding queue, zig-zagging their way towards me. I locked my phone and shoved it in my pocket as sometimes the managers liked to try to sneak up on us. As the couple got about 3 quarters of the way to me I turned around to give them a friendly wave and to assure them that the ride was still open and that they would have the place to themselves. They were gone, I stood staring for a moment in complete puzzlement, there was no way that they could have run out of the room without either opening one of the loud heavy fire doors or jumping over about 20 sets of metal bars that made up the queue. As my brain processed this information the hairs on the back of my neck rose and a sudden chill ran through my very core, needless to say I was very relieved when a co-worker came about ten minutes later so that I could go for my break.
While that was an isolated incident, the next thing happened several times but never really phased me, throughout my life I have had a fair few paranormal encounters and have a certain sense for when something is around, and whether it is malign or not. In the building the Octagon room was the last section of the ruins that guests passed through and believe it or not was a fairly large octagon shaped chamber. Usually after the show finishes a thick, heavy curtain is pulled back by a machine to reveal a secret tunnel that guests must follow. About 4 months into the season this machine broke, and the maintenance staff realized that the part they needed wouldn’t be available until after the park closed in November, so rather than pinning back the curtain the decision was made that one ride assistant would have the fun job of standing behind the curtain in the pitch black and once each show had finished they would pull the curtain and allow the guests to pass through, making sure nobody was left behind.
More often than not, this duty fell to me, I enjoyed my time sat in the dark, after a week or two I knew the exact timings of all the light and sound queues of the show and also scared quite a few people who weren't expecting some guy to be stood behind this mysterious curtain, in fact many people thought I was a wax statue and I would play on this before moving slightly whenever they went in to take a closer look at me. However, every so often I would get an immense oppressive feeling wash over me, the room would feel much darker than it had a couple of seconds before and I would always get the distinct impression that there was some sort of male presence just behind me. Although I never turned around once because f**k that, I always stood my ground, I knew this presence did not want me or anybody else there in his area and he made that quite clear to many other members of staff. There were several reports of female co-workers being pushed from behind while working in that area and even pinched. The frequency and nature of this presence soon meant that I was one of the only people who were willing to stand there and endure the intense feeling of hatred that would randomly appear and disappear, all the while hearing an endless loop of some old hag cackling and whispering curses, I loved it.