Totally coinciding with PAX Prime on purpose, Castle Crashers has been updated with the Pink Knight absolutely free. Bring out your inner Super Sailor Moon and attack your foe with the love power of rainbows. (Shouting "Rainbow Moon Heartache!!!" is optional.)
You can also download the Blacksmith Pack for 160 Microsoft Points and bash enemies with "miniature antlered frogs", but there's plenty of free content to go around: a Team vs. Team arena, two Avatar Awards, and lots of glitch fixes.
$1 will be given to the Keep A Breast foundation for every download of the Pink Knight.