You never know when some viral urban campaign would come around the corner and whack you with some bizarre message.
More interesting ones may even capture your thoughts long after the first visual shock subsides. More often than not, it's just a smart product placement / promotion, but in some cases - truly subversive and genuine urban art.
Streets in Portugal seem to be the most often visited by creative mayhem:
(once you approach these stabbed victims, they will hand you a promo flyer...)