PK3: Unreleased Faraway Island Mew (European Languages) ᅟᅟᅟ

Pokemon Emerald contains a programmed event encounter with the Mythical Pokemon Mew.
However, for the GameBoy Advance version, the key item that activates the event, the Old Sea Map, was only available to the players who played the Japanese version, either for at the Pokémon Festa 2005 event location, or by presenting a Download Certificate (obtained during ticket purchase to M08 Lucario and the Mystery of Mew) at PokéPark Taiwan back in 2006.

This page hosts the Mew that is caught at Faraway Island.
As an extra illegal bonus, it's caught with the Safari Ball, that cannot be obtained outside of the Safari Zone.
 

Update:
It is possible to reach Faraway Island in Non-English and Non-Japanese other European languaged games, using an elaborate usage of glitches, as explained by ChickasaurusGL below.