You need to play this outside, with a good length playing area that has two distinct ends. The ends must be marked out with a line, or a wall, or just two objects on the ground.
One person is the bulldog and stands in the middle of the play area. All the remaining players gather at one end of the area. When the bulldog shouts "Go", everyone must run to the other end without being tagged by the bulldog. If you are tagged you become an extra bulldog and help in the next go. If you reach the other end you cannot be tagged.
The bulldog then shouts "Go" again and everyone dashes back to the other end.
Repeat this process until one player is left as the winner.
Click this animated image!