Bukkit plugin Short Game Mode.
Lets you quickly set/toggle the game mode of any present or past players.
Usage:
/gm # Toggles your game mode
/gm [player] # Toggles [player] game mode
/gm set [player] [mode] # Sets [player] mode to [mode], this works with offline players too
Permission nodes:
sgm.set.* # Umbrella node, gives access to both other and self
sgm.set.other # Allows user to set other players game mode
sgm.set.self # Allows user to set his/her own game mode