One thing I do consider a cheat rather than a strategy is to play Sweeper against Saruo/Saka/Horse Archer types.

Taking an army of almost all combat cavalry (obviously lateish game) and deploying in a single long line stretched across the whole width of the field and just running forwards - they auto withdraw until they run out of room and are then squished. You can do this with Pike Phalanx as well if you spread them out a bit.

This only works because of the battle maps being defined areas.

Not EB but a similar kind of thing in MedII was to declare a crusade and then attack another Catholic faction - you never had to worry about being attacked en-masse as they can't declare a crusade against you. Similarly if on a crusade and about to take the target on your turn you make all of your family members join a crusade no matter where they are, take the target and all your FM's gain bonuses for being successful crusaders even though they never actually left home and were only part of it for less than a turn...