Creating the effect of a Flip Flop gate using Logic Bricks A Flip Flop gate, upon receiving a positive signal, will toggle between a true output and a false output. How can I achieve this effect using logic bricks? 
I want to be able to change perspectives with one key binding from first person to third person in the Blender Game Engine.
From the way you wrote your question, it sounds like you want to toggle between camera views. You can use a Boolean property, and have a keypress toggle that property to true or false. Then, if that property is true, the First Person camera will be activated, and if that property is false, the Third Person Camera will be activated.

This logic setup is one of the simplest you can use to toggle between two camera views:



Of course, you could use an integer property and a few more sensors and controllers to cycle through several camera views, instead of using a Boolean property (which can only be true or false) for the two camera views.