1.) When someone stalks and kills an opponent of yours in front of you thereby depriving you of a kill as in Halo or Call of Duty.
2.) Stalking your roommates when they awake in the middle of the night for a drink or to visit the bathroom.
I would have had enough kills for the EMP if if it were not for the guy nibbleghosting all the time.
I have been nibbleghosting my roommates every night when they get up to pee because the are too out of it to notice me following them through the house.