It's a bit of a trope in war movies that we see dented cigarette tins that saved the life of some lucky soldier who was carrying it in his pocket and it deflected a snipers bullet.
Is there any basis for this in reality and would a tin actually deflect a bullet from a World War 1 weapon?
Unless the bullet was already virtually spent, it's extremely unlikely. The cartridges used in service rifles and machine guns were all (with the exception of the Italians) 7.62-7.92mm, high velocity rounds loaded with aerodynamic and highly efficient bullets. Even without armor-piercing ammunition, they were all capable of penetrating a quarter-inch or so of steel plate. A tin, brass, or mild steel cigarette case would offer very paltry protection against such projectiles, unless the range was so great (far beyond normal combat ranges) that the bullet had been bled of almost all its energy.