With data in ColA try the below macro which will use ColB as a helper column...
Sub Macro1()
Columns(1).Sort Key1:=Range("A2"), Order1:=xlAscending, Header:=xlGuess, _
OrderCustom:=1, Orientation:=xlTopToBottom
Columns(1).AdvancedFilter Action:=xlFilterCopy, _
CopyToRange:=Range("B1"), Unique:=True
Columns(1).Value = Columns(2).Value
Columns(2).Value = ""
End Sub