You're such a mo fo for getting that piece of shit car.
See more words with the same meaning:
My Brother From Another Mother.
A Google employee lied about it.
Of course, the phrase has been around for as long as midlife crisis-stricken dads have been buying motorcycles and Oakley wraparounds, but the YOLO acronym is new.
Which reminds me - I can't believe I missed the American Idol finale last week.
Definition from Wiktionary, the free dictionary.