One huge, ugly, brick wall was - as part of a community project - decorated totally with graffiti by local youngsters in a town near where I live. The finished wall was stunning. It had the usual graffiti of names, dates, slogans etc. but there was also colours and personal artwork by the youngsters - I really loved it and never get tired of seeing it when I pass by. Funnily enough, no one has actually defaced/vandalised this wall at all. It was finished about 4 years ago and still looks great today.