Vikings v Irish in VI when you brought huscarles and no cavalry, especially when it rains or snows...

Anything in the snow when the AI brings tonnes of reinforcements...can i win before my army freezes to death?

AI armies full of Jinettes. Must rank as 'Most Hated Enemy Unit'.

Battles where the enemy army finds the highest point on the map and sits on it and i have no archers.

But most of all...battles where they just will not stand and fight, and it becomes a game of 'chase the AI around the battlefield while swearing furiously'.

Can't remember any specific ones, but battles where you're definitely going to win and then your general gets unluckily killed, resulting in mass routs...they're... annoying.

Good thread. Sharing the pain might help!