I have a soft spot for using projectors in photography. Aside from the art it produces I think that there is something magnificent in using the light in the opposite way while taking a picture, kinda like having a light-dialog.
This is why I love John Lang’s Blind Spot series. John used a projector to throw people’s own faces at them and then take a picture of the (real) composite.
You can read more about John’s work here.