There is only one file type that uses the .UT2 extension:
Unreal Tournament Map
Unreal level map created with Unreal Engine v2; contains the layout the level as well as characters and objects included in the map; used by Unreal Tournament 2003 and 2004.
Unreal Tournament 3, which was released at the end of 2007, uses .UT3 map files.
Updated: July 12, 2009