My favorite example is a working paper by Edward Miguel, Sebastián Saiegh and Shanker Satyanath that uses evidence from professional soccer (football) matches to evaluate whether exposure to civil wars increases the propensity of young men to behave violently. They find that players from countries that have had more exposure to civil wars are much more likely to get yellow and red cards (cautions) than are players from countries that have had little or no recent exposure to civil wars. The findings are substantively strong and robust to a host of controls. The evidence comes from the main European football leagues, which are very cosmopolitan. This strikes me as an example of research that is both clever and important.