Panel:MoveToFront
Example
Creates two frame panels where one acts normal and the other acts as a persistent warning window that will move in front of all other panels until it is closed.
Output: 

Moves the panel in front of all other panels on screen. Unless the panel has been made a pop-up using Panel:MakePopup, it will still draw behind any that have.
Creates two frame panels where one acts normal and the other acts as a persistent warning window that will move in front of all other panels until it is closed.