SAN DIEGO, Nov. 14 - Five artificial-turf paintball fields were laid out like giant green dominoes in the Qualcomm Stadium parking lot here: a setting befitting a sport that aspires to grandeur but that is as yet a funky outsider. But long before you could see the players, goggled and masked and carrying sophisticated militaristic toys, you could hear the chaotic splatting, a joyous flatulence made by hundreds of men, and a handful of women, plastering one another with pink and yellow gobs of goo. An estimated seven million paintballs were being shot by players from the United States, Canada,...