Hi Kagetora,
I'm with Papewaio, I only cheat to balance the game. Sometimes I invade rebel provinces build them up with .worksundays. and then abandon them to the enemy. However this can get you into allsorts of problems when your trusted allies can't resist invading this new juicy province and then all your alliances suddenly fall to pieces due to your kings poor influence.
But rescently I've introduced new income creating buildings, boosted farm revinues and modded the startpos so the AI produces some challenging opponents. Even if they sometimes commit tactical suicide. Maybe one day i'll get into MP and really challenge myself. Cheat codes are fine when your playtesting balancing etc but the game definatley gets boring if you always use them to win. Although it would be nice just to add a thousand florins now and again. But there are ways of doing that if you wanted to.