[Growltigger]

Byzantines are a personal favourite, as are the Spanish.

The Byzantines have some whacky units of their own which are great fun (given that you fight lots of horse archers and camel warriors). The empire is also big and rich so with Constantinople being a Keep as at day 1, you can ramp up.

No infantry kicks the stuffing out of people like the Varangian Guard (except longbows!!)

I also like playing the Spanish - quickly grab Valencia, Portugal and Navarre, launch the reconquista against the Almohads and in the meantime, lauch crusades against the Holy Land (with only a few of your troops, direct the crusades through France and Germany and you will pick up lots of troops) and against any catholic kingdom that gets excommunicated. Battles galore and the Jinetes are great light cavalry.

I also like the Italians, weak militarily (aren't they always) but you can really build up the trade and generate thousands of florins that way...