In rare cases, games that have already been released under one title have had their names changed. The reasoning for this varies from game to game; however, it is especially common for names to be changed due to copyright/trademark reasons.
Infestation: Survivor Stories
Originally released under the title The War Z. The game's name was changed following a release that was met with heavy criticism, largely owing to the fact that the game was released in a state in which many of its advertised features were missing. Its premise and title were also criticized for their thinly-veiled imitation of DayZ, a popular ArmA II mod that at the time was being developed into a full retail product of its own. The game's name was changed to Infestation: Survivor Stories in order to distance it from that criticism.
Originally released under the title Trenched in North America. In Europe, however, the game's release was stymied due to the fact that the title was already the property of a Portuguese designer of a board game called Trench. Due to the specifics of European trademark law, the trademark holder also owns the rights to variants of that name, including Trenched. As such, Microsoft, the publisher of Trenched, was not allowed to release the game in Europe under that title. Thus, the game was released as Iron Brigade in Europe. However, due to a quirk of Xbox Live, North American players of Trenched and European players of Iron Brigade couldn't play together, and so the North American release was renamed with the Iron Brigade branding in order to ensure compatibility.