1Up has a short and sweet article on the Top Ten Game Clichés that must die!. Among them, one of my personal favorites:
Exploding barrels
Again, a little warehouse management can go a long way. You work in a field that's prone to random assaults and frequent gunfire, yet you spot your adversaries some free bombs in strategic locations. Some of you even tell your henchmen to hide behind them for cover. And if you survive Johnny Rambo's attempt to take you down, good luck getting hazard pay.
Exploding barrels
Again, a little warehouse management can go a long way. You work in a field that's prone to random assaults and frequent gunfire, yet you spot your adversaries some free bombs in strategic locations. Some of you even tell your henchmen to hide behind them for cover. And if you survive Johnny Rambo's attempt to take you down, good luck getting hazard pay.