Battlefield Heroes players can input the following code to earn double the XP they normally would for playing: 5RH4-G9WR-MVV2-Q4E7. Just enter the code on this page, then it's off to the races -- er, the battlefield, rather.
You've got to give it up to DICE, who has managed to keep its free-to-play shooter fresh through steady content updates -- the latest of which includes a new map and mode centered around jetpacks. And that, folks, is how you enlist over three million players.
[Via Big Download]