Didn't see it, but a bunkmate woke up in the middle of the night during our recruit training phase and decided to listen to some music on his MP3 Player. He turns to face away from the dimly-lit corridor while lying down and sees the reflections of 3 sillhouettes dashing by at superhuman speed in the window in the direction he was facing. They then dashed by a few more times and he, for some reason decides to check to see whether they're ghosts or otherwise. He moves toward the door, it suddenly opens into his face as two other bunkmates (I must emphasize that they showed no signs of having been running around, according to the first bunkmate of mine) returned from the bathroom. The two of them swore they were walking, and saw neither whatever those things in the corridor were nor the bunkmate who went to check them out. Said bunkmate was majorly freaked out by the incident.
As for me, I've never experienced paranormal activity. As to whether I believe it or not, for me the possibility remains; I will, however, wait for evidence of their existence.