I Remember Reading This Phrase From A Long Time Ago,

"When his pin is pulled, Mr. Grenade is no longer your friend!",

the reason I remembered the phrase is because I came across this 1918 athletic training guide, aimed at branches of the Knights of Columbus, a Catholic fraternal organization in the United States, if you think about it many sports can actually trace their origins to warfare, and hand grenade throwing could be the cursor to a few, the copy was tracked down by Weird Universe, 

the United States was mobilizing, so it was necessary to get as many young men ready for modern combat as quickly as possible. Sports should therefore reflect battlefield needs, so Captain Lewis Omer of the newly-formed 86th Infantry Division proposes that young men practice grenade throwing as a sport, and here is how it is played, the player is inside a cage simulating a trench. In sixty seconds, he must throw as many grenades as possible into boxes at different ranges representing enemy trenches. Between each throw, he must hit the ground, touching his knees and his chest to floor of the cage, close, counts in horseshoes and hand grenades, so land the grenades as close to the target as possible for maximum points,

immediately after the section on grenade throwing is a description of Trench Ball, an adaptation of football for trench warfare, but with any number of players on one side between 10 and 250, it must have taken some organising, still both sound like fun, and I guess to liven things up Mr. Grenade really could have his pin pulled!