Quote Originally Posted by Sin Qua Non
Maginot Line, 200BC: Set up a fort line with 4+ onagers each. When the hapless AI needs to attack the forts to get to your soft, chewy heartland, you sally forth, fire the onagers until out of ammo, then end the sally and repeat ad infinitum (or more likely until the enemy lies in orderly piles). This evil little exploit works wonders in invasion-heavy traffic areas, and when you are ready to push the line forward, you will have plenty of gold chveron onagers to attack cities with!

So delightfully evil, that you will probaly do it for one game before swearing it off!
Love that one