The William Kaufman organisation had the right idea when it built an office tower at 77 Water Street in New York City. Instead of installing drab air conditioning units on the roof, the company plopped down a 1917 biplane.
The company didn't do it for kicks, they did it for their neighbours who have to look down on the pint-size building. The WWI British Sopwith Camel is an artistic re-creation that was hoisted by crane to the top of the building in 1969. To the delight of those nearby, the plane has stayed there ever since.
This isn't the only example of creative building design by the William Kaufman organisation. Other buildings owned by the company include a rooftop penny candy store and a tiled picture of a cat chasing a canary. [WSJ via Laughing Squid]