I shared a small 2 bedroom apartment several years back with a good buddy. We had lived there already about a year and a half and never had any incidents until this one night I had just drifted off to sleep and it felt like someone or something sat down abruptly at the end of my bed, the pressure was such that it startled me to awaken. I quickly brushed it off that it was me jerking as sometimes people do when they are drifting into sleep.
Later that same night at about 3am I awoke to a light knocking at my door and assuming it was my roommate I asked "What's up? Come in." I said this twice and nothing happened so I got up to open my door which had a direct view down the hallway toward the other bedroom and only bathroom in the apartment. When I opened the door I caught a shadowy glimpse of a dark figure standing in the hallway that then proceeded to leisurely walk into the dark bathroom after which no light went on.
Thinking that was odd I called out to my roommate as I walked down the hallway. As I approached the end of the hall the first thing I noticed was my roommate in his bed sound asleep snoring and this made the hair on the back of my neck stand up because I saw someone go into the bathroom. I stopped in front of the dark bathroom and slowly walked in and turned on the light, there was no one there but I immediately was taken back by a pungent sulfur smell that made me back up quickly and cover my nose. It was genuinely repulsive and I can't tell you how fast I skedaddled back to my room and jumped in the bed. I wasn't able to fall back sleep until the sun came up.