Show your work in the comments section. My votes? The American Revolution (more because of what it did for human freedom after the fact–not sure I would have supported it at the time), World War II, and Afghanistan. And I guess you sorta’ have to include the War of 1812, too. I’m torn on the Civil War, because I’m not sure slavery wouldn’t have died out on its own without 600,000 people dying in the process.
NOTE: There seems to be something amiss with the way PollDaddy tallies multiple choice surveys. So have it at it in the comments section. But the poll results aren’t right.