This is going off-topic, but one of the original pathfinding ideas I have read was scent-based. Basically the character smells and his smell spreads aound him in every direction (not through walls of course). The smell is also left behind him and it slowly fades away after he has moved away. Now the enemies have nose and can detect which way the scent of char is stronger to move that way. Have not seen that idea in action, but still liked it because it is more realistic then simply finding path through invisible walls.