SimplyGM

Made for personal use but I figured why not share. All this plugin does is change your gamemode with the commands:

/gmc (for Creative mode)
/gma (for Adventure mode)
/gms (for Survival mode)
/gmsp (for Spectator mode)

Permissions are:
gamemode.<name> (Personal Use) Example: gamemode.creative
gamemode.<name>.others (To use on others)

Players and Console are notified when they use the command. Targets of the command are not notified.