I love movies as much as the next person, but many scenes get things like weapons, tactics and technology so wrong. I have been involved with technology since I was a teenager and was in the British military for 20 years, so I can speak with some authority on some subjects below.

Weapons

1. Scene: Good guys are hiding behind the sofa or in a wardrobe, bad guy enters the room with some kind of assault weapon and sprays the room with bullets (rounds), good guys walk out unscathed.
   
   Truth: Most bullets will go through several inches of wood, clay pots, TVs, computers, stereos and most white goods. Even breeze block can be penetrated by high-velocity rounds and cars aren't safe either. The only things that might protect you are brick walls, engine blocks or wheel hubs.
   
   
2. Scene: The good guy aims a pistol at the bad guy who is over 100 meters away, shoots and hits them.
   
   Truth: Pistols are short-barrelled and usually fire low-velocity rounds making the effective range about 30 ~ 50 meters. Special forces might, with their advanced training, hit further away but not that much.
   
   
3. Scene: Someone fires their weapon and eventually empties the magazine. They pull the trigger and the weapon clicks, They pull the trigger again and again and the weapon clicks again and again.
   
   Truth: There will be one click only when the hammer flies forward and strikes the firing pin. As there is no round in the chamber there will be no breach explosion just a click. Pulling the trigger again won't achieve anything because the hammer is still forwards.
   
   Most weapons use the breach explosion to propel the round forwards and to push the breach-block backwards, ejecting the empty case and pushing the hammer back. A spring moves the breach-block forwards and feeds the next round from the magazine into the chamber ready to be fired. On some pistols the slide stays to the rear when the magazine is empty, allowing the firer to remove the magazine, replace it with a new one, release the slide and carry on firing.
   
   The exception to this are revolvers which work a lot differently.
   
   Offenders 24.
   
   
4. Scene Someone throws a hand grenade into a room and the whole building erupts in a huge ball of flame.
   
   Truth When a normal hand grenade explodes there will be a flash, a bang, some smoke and anyone within 30 feet (approx) will be hit by shrapnel and probably killed. Most grenades don't have enough explosive power to take down a whole building
   
   Offenders Most action movies.
   
   
5. Scene Doctor explains that there is a 7.62 mm round lodged in the victim's leg.
   
   Truth 7.62 mm rounds are high velocity and extremely powerful. They will go straight through flesh, muscle, bone and will still have enough energy to go through several more victims.
   
   

Tactics

1. Scene: Big shoot-out, lots of people firing various weapons at each other. One guy in frustration gets up from behind cover and sprays the enemy with his machine gun. He is quickly killed.
   
   Truth: No trained soldier would ever do this (for the obvious reason) and spraying bullets randomly probably won't hit anything, especially if the others are behind cover.
   
   Offenders Most of the bad guys from any movie !
   
   
2. Scene During the shoot-out, the main star (who is a high ranking officer: Army Colonel or Navy Captain / Admiral) leads the charge, in fact they seem to be doing everything.
   
   Truth Despite Hollywood's insistence that their star should be in almost every scene, high ranking officers wouldn't be anywhere near the front line, it would be lower ranking officers that would be engaged in shoot-outs / fire-fights.
   
   Offenders The Last Ship
   

Technology

1. Scene: Hacker finally gains access to a server and is presented with a dazzling display of animated 3D graphics.
   
   Truth: The display won't be any more dazzling than this one !
   
   Offenders War Games, Weird Science, Swordfish.
   
   
2. Scene: Good guy #1 says "Quick, trace that mobile phone call." Good Guy #2 says "It will take 30 seconds so keep him talking for as long as you can."
   
   Truth: The mobile phone network knows roughly where your phone is whether you are talking or not. The exception would be if you remove the battery.
   
   Offenders 24.
   
   
3. Scene a malfunction cases a computer to explode and/or burst into flames."
   
   Truth Computers just don't do that.
   
   Offenders Scanners.
   
   

That said here is a video entitled "Best Hacking Scenes in Movies" which seems to be a mix of good, bad or plain idiotic - enjoy



Here is a video of Simon Whistler talking about how Hollywood gets military life so wrong