The Mk82 is a 500lb unguided bomb. Two versions exist, where the regular Mk82 is a simple free-falling ordnance. The SnakeEye version adds a tail section which deploys into airbrakes, making it better suited for low-altitude bombing runs.
Bahamuto Dynamics in Real Life Edit
It's cheap cost and reliability has led the Mk82 to become extremely common, and has had over 40 years in active service.