Classification: Usually a misdemeanor 
Probability: Low

With New York's anti-graffiti task-force in constant motion, it's unlikely that you'll see more than a few sharpie tags on a modern subway train. That said, graffiti was once one of the great scourges of the city's public transportation system. Now, the times when a street artist manages to bomb a whole rain are almost non-existent. One exception is Barcelona's OTP Crew, who hit some trains in the Bronx recently. While it's probably better that our cars are now cleaners, there's still a certain nostalgia to seeing a neon-slathered subway car.