Saints Row 4, available now on Steam for $2.99. The pack features giant club and bone weapon costume, caveman outfits for male and female characters and a "Flintstone's like car."
For those worried, Volition promises the DLC features "100% historically-accurate" content. Based on the pictures of said content, we're inclined to believe them. So, go forth my sex toy-swinging friends and have a gay old time with one of Joystiq's favorite games of 2013.