1. Last Hope to save whichever fictional nation
2.
Amnesia/piecing together whatever may have went down. . . .
3. Fighting your way through a specific location, then having to fight your way back out of the location. Basically
backtracking 
4. Killing a boss only to have him turn into some unknown/unseen uber boss.
5. And the worst to me; Game starts up , you are all badass with all of your abilities, then something happens causing you to spend the entire first half of the game searching for your lost gear/abilities.