My favorite seige was actually defending. I had about 700 of my Seleucids against some 1100 Macedonians. My army was mostly militia phalanx with a few cretan archers. In a nutshell, they made three holes in the walls, ran in, started killing...my militia fought to the bitter end. But the best part was putting a phalanx in a road, another dead behind it, and the last units of cretans behind that, and then watching wave after wave after wave of Macedonians charge under arrow fire, break, reform, charge. Eventually a lone cavalry unit snuck in from behind and the fighting went to hand to hand on all fronts. Cretan archers were the last to be killed as they went to melee against a unit of levy pikemen. It was just awesome to see street fighting work out so well.