Perhaps this is a self-portrait of the artist who painted this mural? He at least appears to be friendly with his big smile.
Here's a better look at the wall, it's really quite a large area! This one is on the side of a building near an S-Bahn station in Schoneberg. More murals can be found at Mural Monday.
PS: I'm posting more regularly on Halcyon Travels. Please stop by and take a look.