Creatively "edited" speed hump sign in the 1400 block of Monroe Street NW, in Columbia Heights. The fact that the graffiti artist made a blatant grammatical error makes this even funnier than if executed to say Speed Humpin'. Personally, I would have gone for the whole -ing suffix. 
Every time I go past this sign I laugh a little. My brother was amused by the sign the last time he visited, as well. We're immature, what can I say? Normally, I really dislike graffiti, but this is cute. The only other instance of graffiti I've approved of was the "Surrender Dorothy" painted on the Beltway overpass in sight of the huge Mormon Temple in Maryland. It has been gone for years, but the temple does look like Oz...