百合・D・ルフィバグ修正
Sub Macro2()
  Dim d As Object
  Set d = CreateObject("Scripting.Dictionary")
  rr = Cells(Rows.Count, 1).End(xlUp).Row
  For r = 1 To rr
    For i = 1 To rr
      If Cells(i, 1) = Cells(r, 1) Then
        s = Cells(i, 2)
        If Not d.exists(s) Then d.Add (s), 0
      End If
    Next
    Cells(r, 3) = Join(d.keys, "・")
    d.RemoveAll
  Next
End Sub