Exploding barrels.
Firstly, no matter whether you're in a military complex, a zombie-infested city, or just driving around a replica of downtown LA carjacking people, if you ever see a barrel lying around, you know that it will be filled with some sort of flammable material.
What are these barrels doing everywhere? And would one even explode as soon as you shot a single bullet at it?
Regenerative health
How many people do you know that would survive a bullet at point blank range without even falling over?
It really frustrates me when I've been chasing an enemy down for 15 minutes, finally rain down a barrage of bullets on them, only to see them regenerate back to full health after crouching down behind some boxes.
You sustain fatal wounds and all that happens is your breathing gets a little heavier?!?
Wouldn't it be cool if a direct shot to a limb with a shotgun actually meant the player lost that limb? What about blood loss from all those open wounds? Could that be incorporated into games?
Overly dramatic cut scenes
So I've been rushing armed guards, fighting off swarms of aliens, and dodging explosions left, right and center - then suddenly someone pulls a gun on me during a cut scene and the music turns dramatic.
In Far Cry 3, you somehow survive bullets, stab wounds and being set on fire by armed militia - and yet during one hostage cut scene, two men are able to restrain you and sever your finger and your character actually passes out. Talk about drama queen!