http://textmechanic.com/Remove-Duplicate-Lines.html
#include <Array.au3>
#include <File.au3>
#include <FileConstants.au3>
Local $out, $i, $unique, $arr, $in = "c:\test.txt"
_FileReadToArray($in, $arr)
$unique = _ArrayUnique($arr)
$out = FileOpen("c:\test_unique.txt",$FO_OVERWRITE)
For $i = 0 To UBound($unique) - 1
if ($i >1) Then
FileWrite($out, $unique[$i] & @CRLF)
EndIf
Next
FileClose($out)