Rembrandt's 1642 group portrait of members of an Amsterdam militia is one of the most popular paintings at the Rijksmuseum in Amsterdam, drawing about 4,000 to 5,000 visitors daily, but it certainly has ticked off a few patrons. First, in the early 1900s, an unemployed navy cook attempted to slash it with a knife — for no apparent reason — but was unsuccessful in getting through its thick varnish. In 1975, a disturbed man named William de Rijk returned to the museum a day after being turned away because he'd arrived minutes after closing and allegedly exacted revenge by cutting zig-zag lines into the painting. The artwork was restored, but some say remnants of the damage can still be seen. Fifteen years later, a mentally ill German named Hans-Joachim Bohlmann — who had a history of attacking works of art — threw acid on the piece; security guards were able to quickly dilute it with water so that the acid penetrated only the varnish layer of the painting. It was restored once more. The Night Watch was valued at about $925,000 following the second attack; no word on how much the beat-up painting would fetch today.