There is only one file type that uses the .MRS extension:
GunZ Game Data File
Stores game data used by GunZ (a.k.a. "GunZ the Duel"), an online multiplayer action game; stores information such as weapons, clothing, spawn points, number of players per room, and other data; may be decompiled and edited with a program called MRS Decompiler.
Players can find and join live GunZ games at ijji.com.
Updated: November 6, 2009