If you have an xbox or a windows computer check out http://fuse.microsoft.com/kodu/ it is a really simple game development tool.

It is a visual event based system.

You have a queue of events. You then define relationships. Events at the top of the queue take priority over items lower on the queue. There is also the ability to define multiple queues and switch between them.

Relationships are simple but can be used to build complex systems.