Danish: "øf! øf!" (Courtesy of skongshoj)
Dutch: "knor knor" (Courtesy of BurningTongues)
Finnish: "röh röh"
German: "Grunz, grunz" (Courtesy of gwenllian)
Hebrew: (Undone will have us note that there is no such thing as a good Hebrew pig for kosher reasons.)
Hungarian: "röf-röf" (Courtesy of ba)
Norwegian: "Nøff nøff" (Courtesy of Sverre)
Portuguese: "óinc óinc" (Courtesy of e-anorexia.)
Spanish: "oink! oink!"(Courtesy of koala)
Swedish: "nöff nöff" (Courtesy of rollo)
please /msg p_i with further contributions to this (or other aspects to noises animals make in different languages), assuredly the best use yet found for the global forum that is the Internet.