http://www.gearboxsoftware.com/community/articles/1005/happy-loverpalooza

PC Shift Code: W3KJ3-69JR5-9CXT3-JTJJT-WSCK5

This year's offerings include special celebratory skins -- "Real Men Wear Pink" for Axton, "Tiptoe Through the Tulips" for Zer0, "Pretty and Pink" for Maya, "Pink Eyes" for Salvador, "Gumming the Works" for Gaige -- that will be available in the Quick Change character customization station, along with a special version of Moxxi's Heart Breaker shotgun that will be the same level as (and appear in the backpack of) the first character you load after redeeming the code.

These codes will be active through February 17, 2013 -- be sure to use them before then!