Sometimes you have to rip the rug out from under the players and take them for surprise. Sometimes you try and the players see it coming from a mile away. Games where at the end the PCs find out they were the villains all along. Games were PCs know what is going to change, but still go with it. The change of pace, change of direction, can still be a lot of fun.
So what is your favorite one?
For me, it probably goes back to the end of a game I was in years ago. In the last mission it became clear to the party that their boss wasn't actually playing for the right team. Suddenly the person who knew everything about them, brought them together, and gave them purpose was the enemy. Could the group out plan that person? Could they succeed? It made the next few sessions very tense and interesting, and made for a solid ending.
What about you?
Also, while I have you, there will be no posts next week. I'm going to be out of town on a business trip and won't have reliable access. If I can get something up I will, but I'm going to assume that I won't be able to.
Have a good week!