that would be
Super Challenge Baseball from Intellivision, Inc. (later bought out by Mattel)
The shape is like an old Intellivision cartridge that the company simply modified to fit the 2600. I think this needs to be added to the database. The M Network version of this game has the full title on the end, but in blue text on a black background, and the Telegames version is more like a normal 2600 cart with a big ugly white label on the side.