Paint, black pen
Alexandre Orion is a Brazilian tagger that got famous doing clean tags of skulls in a tunnel of Sao Paulo.
The concept can not be easier, with a rag and some water, Alexandre removed the black dust from the dirty walls of the tunnel, and there it goes.
Obviously the police cannot arrest anyone for cleaning up the city..
And how did the city council get rid of the tag? ... By cleaning up the whole tunnel!
It happened in 2007, but it took quite some time to get to my ears ^^
isn't it so cuuuute?!
(yeah, im a girl and a cat-lover, i admit that otherwise it doesn't work that well..)