GCA
From Just Solve the File Format Problem
GCA is an archiving format developed in 2000 by Japanese programmer Shin-ichi Tsuruta. It is mostly used in compressing characters from the M.U.G.E.N game engine. It is optimized for compression ratio for binary files. DGCA was released later as a successor to it.
Identification
GCA files start with ASCII "GCAX
".