1.
Something that slowly walks around on the ceiling, always looking at the floor, with a light showing what it can see. If it sees the player, it jumps down and kills them.
The only way to avoid being seen is by hiding under something, like a box.
It would be completely deaf.
2.
Something that floats around rooms. Upon touching the player, the player would be frozen in place for a second as the thing attaches the player to the floor.
It would do no damage, and would disappear after stopping the player 3 times.
It wouldn't follow the player.