Well, this is a bug/exploit left over from RTW, but now manifesting in a new and shiny way:

I had my crusade army board a ship from England to reach Antioch, and on their second turn of movement I discovered I actually had unlimited movement - I moved the ships from the west coast of Spain all the way to the coast of Antioch in one go. All I did was select all ships in the fleet after there initial movement points had run out, and I kept getting a renewed movement range, even though the admiral kept saying 'no more move' etc, each time the fleets reached the end of their 'new' move allowance.

I'm not sure if the following is a bug or just a cheesy exploit, but when playing as the English you can deploy longbow stakes inside fortresses during the deployment phase and thereby massacre any cavalry that comes through the gate. I think the deploy stake ability should be removed in siege maps. I know I could always not use this ability, but removing it removes temptation!