.OMOD File Extension
What is an OMOD file?
Game file used by Oblivion Mod Manager (OBMM) and Nexus Mod Manager (NMM), two programs used for applying game mods to The Elder Scrolls: Oblivion and Fallout 3; contains the data files that alter regular game content; saved using .7Z compression.
OMOD files are used by game community members for creating custom game content. For example, a mod may change the properties of weapons or the appearance of scenery and characters.
NOTE: Both OBMM and NMM require that Oblivion be installed in order to apply mods.