Our company has been located at our Richmond, Virginia office building for almost 15 years. For years (as long as we can remember), we've felt a "presence" in the office -- especially at night time. We heard all of the creepy sounds of someone walking around, the banging noises, etc. We've seen the lights flicker on and off, and someone thought they spotted an "orb". We've "felt" someone in the room before... Even had an experience where it felt like someone got "grabbed" from behind.
We have two doors on the front of our building. One we use as our main entrance. The other door we keep dead-bolted. It never gets unlocked.
On Sunday, December 2, 2012, I came into the office early to get some work done. I left around 11:30am, and received a phone call from my boss at 3:30pm. He told me he just came into the office and wanted to know why the door (that always stays dead bolted) was opened... Wide open. I told him I was over by that particular door (the coffeepot is next to it), but never touched the door. My boss did a perimeter run to make sure that no one had broken in (there was a break-in several months back), but he didn't see any signs of anything being taken, etc.
He then pulled up one of our cameras that we have angled at that door. Around 2:52pm, the dead bolted door did open... But not with anyone's help. We can't explain it. We've zoomed in and reviewed the video several times. This door opened... And there was no one there.