You duck behind a wall and notice that you're standing on top of a shotgun. You're secondary is out of ammo... What do?
Now, take note that there is a fully shielded spartan coming around the corner armed wielding an Assault Rifle, and you're shields are low. One punch could tear you apart, so you have to make the kill certain.
If you stick with the sword, you would have more of a chance of killing him, and a longer range of doing so. Also, it could be quicker, because you're using the scout class, because you can sprint up to him and quickly press punch when close enough, and you wont do the "Pulling up weapon" animation. but if he happens to land a punch as soon as you hit your slash, it will kill you, and he will only loose his shields. There will be massive tea-bagging to occur.
If you pick up the shotgun, the only way he will kill you is if the first shot doesn't land. You have to make it count, and since he has full shield, you should get as close as possible. Sprinting will cause the "Pulling up weapon" animation, and get you killed
Your HUD is flashing, and an ongoing beep is warning you to stay low. But he will find you if you try to hide, you HAVE to kill him now. He's coming around the corner, quick, make your move