what makes the weeping angels so scary, is that they're everywhere. they can't move when someone is wathing them....but then they almost can't be destroyed either. when no one is looking at them, they're scary fast.
With a touch, a Weeping Angel can send a person into the past, to before his/her own birth. The Angels feed off the "potential energy" of the years their victims would have lived in the present. The Doctor describes them as "the only psychopaths in the universe to kill you nicely" because their victims are otherwise uninjured and may live out their lifespans in the past. They can drain other forms of energy, such as that from electric lights, as seen in the Season 3 episode "Blink", or other electronics. Without power, the Angels start to decay, turn to stone without being watched, and corrode as a statue does; their speed is also extremely hindered if Angels reach starvation, as seen in The Time of Angels, lessened from meters to a partial step in a blink. This can be undone by providing the Angels with energy, but it is implied they can no longer acquire energy themselves in this state. In "Blink," the Angels stole the Doctor's TARDIS after trapping him in the past. The engine of the vehicle contained enough energy to feed them for a lifetime.
They have also exhibited the power to project themselves through images. In "The Time of Angels", an Angel trapped in the vault of the Byzantium is able to control a video screen that was playing video footage of it. It overrode the screen controls and could control nearby electronic equipment as well. The Angel is able to take over the screen and come through it in an attempt to kill Amy because "that which holds the image of an angel becomes itself an angel", from a warning in an ancient book on the Angels, found by River Song.
Weeping Angels can plant an image of themselves into a person's mind by looking straight into their eyes. Amy Pond was infested in such a manner where an involuntary verbal count-down indicated her open-eyed moments left as a human. She was able to suspend the Angel's gestation, though not eliminate it, by closing her eyes, refusing to let it breach the 'filter' of her optic nerve.
sorry....was faster to copy/paste......