For those born without a sense of humour, Halopedia has an article on Dadab.
Lighter Than Some Dadab
Dadab is a grunt who single-handedly almost killed Tartar Sauce, defied the Prophets, talked to a booger in sign language, destroyed a dropship with an escape pod, preached about the great journey, and got crushed by the Fist Of Rukt all in one week.

His body was later found by the Prophet of Lies (The Prophet Of Truth's brother) who with the help of Margaret Parangosky revived him. He then discovered Gruntiness and wrote a best seller about it. He now lives in Bill Gates' basement and is planning a hostile takeover of Microsoft through the the stock market.