In one of my history classes a teacher showed us this form of Graffiti, i had never seen or heard of before i thought it was really interesting. It's called Laser Light Graffiti. It's obviously not permanent, but it allows the Graffiti to be placed on a much larger scale. It's also not damaging or degrading. I think it's pretty sweet.
You can find more information at Graffiti Research Labs.
There is also a youtube video which demonstrates the performance.