There is only one file type that uses the .XGT extension:
Exient Texture File
An XGT file contains a texture used by a game using the Exient XGS Engine, which includes Angry Birds Go! and Angry Birds Transformers. It may contain uncompressed image data in the RGA 8888 and RGBA4444 formats or compressed image data in the ETC1, DXT1, ATSC and PVRTC formats. XGT files are used by the game to apply a texture to an object in the game.
XGT files are not meant to be opened by a user. The XGT files are packaged with games and are referenced by the game.
Updated: September 25, 2019