haha, that urbandictionary.com link is da bomb!
fo' shizzle my nizzle
"'fo shizz-ul my nizz-ul'"
"fo shizzle ma nizzle" is a bastardization of "fo' sheezy mah neezy" which is a bastardization of "for sure mah n!gga" which is a bastdardization of "I concur with you whole heartedly my African american brother"