A spelling of Uyghur that looks kind of like the word nigger and therefor is funny because it looks like the word nigger and everybody knows anything that has something to do with the word nigger is utterly hilarious
"Not all Uiggers are bad, most Uiggers are, in fact, normal peopletrying to live a peaceful life in our harmonious society, but them ISISoid ones, man fuck those bastards."
The name for someone who is particularly ugly, but you still regard as a friend. From the point of view of the ugly person that the term 'uggerz' is aimed at, it's not seen as being very offensive, more of a strange nick name.
ie A friendly name for a really ugly person