Exploding cars - Gasoline doesn't explode unless mixed with about 93% air. This might shock you, but if two cars crash into each other, they won't explode instantly. If a car flips over, its driver doesn't have to rush out of it in seconds, because it won't likely explode. Shooting a gas tank won't make the car explode, either.

The speed of sound - Thunder follows lighting, usually after a few seconds, depending on how far you are from where it hit. They don't occur simultaneously. The same goes for volcano eruption which won't be heard immediately rather than five seconds later for each mile. Explosions on the battlefield? You would hear them with a delay, not instantly, like in the movies.

Grenade explosion - Unlike in the movies, a grenade won't explode into a huge cloud of fire. Grenades are not bombs. The most damage from a grenade is done by its shrapnel. The base concept here is that a grenade explodes, launching metal parts around it.

Radioactivity - Exposing yourself to radiation won't make you glow in the dark. That's not how radiation works. It is also NOT contagious - the radioactive particles must stick to you to make you radioactive. Radiation emits light when it encounters phosphor. It doesn't glow by itself.

Artillery shells - Artillery shells blow out, killing people around them. When you see actors running through a field, dodging shells, blowing up around them, you might think that's how they work. Wrong. They have a large and effective range as well as a deadly blast radius.

The sparking bullet - The sparks of a bullet coming out of a gun might look effective, especially in slow motion, but that's not how bullets work. Bullets are designed not to scar the steel of the gun barrel. Meaning: no sparks fly from the front of the gun in reality.

Slow Mo sound - In reality, if you slow down motion by a factor of two, the frequency of all sounds should drop by an octave. Sound is an oscillation of the air. Despite this fact, in many movies you can see the action slow down, but you can hear people screaming in their normal voice.

Sound in space - As you can read from the poster for Alien: “In space, nobody can hear you scream.” Sound is the vibration of air, and it’s sensed when the air makes your eardrums vibrate.

Kicks don't send targets flying - In reality momentum is conserved, such that every action has an equal and opposite reaction. If you see someone kick their opponent, or even shoot them from a shotgun, and make them fly a few feet, even if the kick/shot had enough power to do so, it would send the kicker/shooter flying in the opposite direction. Physics.

Jumping the gaps - During the 1989 San Francisco earthquake, a driver saw a gap in the bridge, and probably inspired by the movies, accelerated to try to jump over it. He fell into the hole and crashed on the other side. A bus can't jump over gaps in bridges, even if they go heavy on the accelerator.