The Game of the Year Edition contains the full version of Guild Wars Prophecies, and was released one year after the game's initial release. It contains an access key which unlocks seven exclusive weapons and accessories, each geared towards one of the six core professions. Each weapon has maximum damage stats according to its type, and each character created can get a customized copy of the weapons. This version was released as the One Million Edition in Europe and is also available as an upgrade to any earlier Prophecies editions via the online store.
Source: Wikipedia, "Guild Wars Prophecies", available under the CC-BY-SA License.