The enemy AI in Monolith’s 2005 shooter F.E.A.R. is still cited as among the best in the genre - soldiers flank, take cover, suppress, and flush the player with grenades. Yet, as lead AI programmer Jeff Orkin revealed in his GDC 2006 paper “Three States and a Plan,” the character finite state machine had “only three states”: Goto, Animate, and UseSmartObject. Orkin even notes that since UseSmartObject is “really just a specialized data-driven version of the Animate state,” it is “really talking about an FSM with only two states.”
The apparent intelligence did not come from a sprawling state machine. It came from a separate Goal-Oriented Action Planning (GOAP) system that used A* to plan sequences of those few actions toward goals. The tiny FSM just executed whatever the planner decided.