Hacky Pinky is a legendary gladiatorial contest that was banned from every school in Scotland but which was played daily under the guise of its poofy subordinate British Bulldog.
In short most of the entire school would split into two teams who ranged themselves against each other at the farthest extremities of the playground much in the manner of Zulu warriors. One then waited whilst the decision makers (hardest kids) on the other team chose a victim from your team and called out their name.
In a nightmare enducing moment the other team would then chant your name over and over again until you made your run after you had effectively chosen the instruments of your own torture by having to nominate two kids to try and stop you. Here lay the essential difference between Hacky Pinky and British Bulldog. In the latter the opponents merely had to 'tig' you to get you out and amalgamated with their team. In the former the two basically beat the shit out of you until you went down.... and then amalgamated with their team. If you made it across the whole of your own team rushed across to meet with the opponents who also rushed across culminating in a sort of Armageddon. Scenes ensued reminiscent of Passchendale and the Somme. (ed: thanks again Chris)