OsAvatarStopAnimation
From OpenSimulator
osAvatarStopAnimation(key avatar, string animation)
This function stops the specified animation if it is playing on the avatar given. The value avatar is a UUID, and the animation value is either the name of an animation in the task inventory or the UUID of an animation. If the specified avatar is not logged in or on the same sim as the script, then osAvatarStopAnimation silently fails.
osAvatarStopAnimation has a threat level of High.