Whoever has this as a last name is generally a L33T nerd fighter. If you have this last name then you are most likely retarded and there is nothing you can do about it.
However, everyone loves McArthurs =D
Person 1: "What's that guys last name?"
Person 2: "Uhm...I dunno, he's pretty awesome and kinda retarded. But I like him."
Person 3: "Must be McArthur"
Person 4: "Yeah, I bet."