There is only one file type that uses the .MANI extension:
Mine-imator Project File
File created by Mine-imator, a program used for making Minecraft animations; used as a project file and contains the animation timeline as well as the mobs, items, and terrain for the scene; can be exported to an .AVI video when complete.
Mine-imator can be used for making Minecraft movies published to YouTube and other video sharing websites.
Updated: February 8, 2014