var
  sl : TStringList;
begin
  sl := TStringList.Create;
  with sl do
  begin
    Sorted     := True;
    Duplicates := dupIgnore;

    //
    // add your items here
    // all the duplicate items
    // will be ignored
    //
    Add(Input1.text);
  end;

  //
  // now you can assign the
  // string list with unique
  // items to listbox1 (example)
  //
  ListBox1.Items.Assign(sl);
  sl.Free;
end;