Improbable Cover

The rule of Improbable Cover states: explosions in movies can't see you if you sidestep behind a wall or jump behind a table.

Of course, as the MythBusters showed, this can be Truth in Television often some small amount of cover can blunt the "pressure shockwave" caused by the explosion, although insufficient cover probably won't protect you from flames or flying debris also caused by the explosion, which can still injure or kill you.

Sister trope of Concealment Equals Cover. Also see Bulletproof Human Shield.

Manga and anime

 * Barefoot Gen, Gen survives the detonation of the nuclear bomb simply because there was a wall between him and it. The people around him were not so lucky. Even more terrifying because it actually happened....

Film

 * In Double Team, the heroes hide behind a coke machine and survive despite roaring walls of flame on either side. Possibly a moment of genre-savvy
 * Independence Day: Pretty much every time there's an explosion that the heroes escape, they do so by this trope.
 * Predator and Predator II. In the first film Dutch lives through a small nuclear (?) explosion at close range because he ducked behind some cover. In the second film Lieutenant Harrigan survives the exhaust blast of a Predator ship taking off by doing the same thing.
 * In Hot Fuzz a massive explosion that takes out a whole building is survived by the people inside it. They do this by how they did this is 'explained' in the extras.
 * Dante's Peak: Harry, Mayor Wando and her kids escapee the eruption of the titular volcano by hiding in a mine.
 * The Day After Tomorrow: they outrun an oncoming ice storm, and escape it by closing a door.
 * In the Die Hard, series, this hapens multiple times.
 * In the first film, McClane builds a homemade bomb and tosses it down an elevator shaft. When it goes off, a blast of fire shoots upword toward him. He survives by stepping to the side of the door.
 * Which is a rare justified example of this trope; McClane is hundreds of feet away from the center of the blast, and the only reason its still dangerous to him at all is because the elevator shaft is funneling it towards him. Step away from the 'mouth' of the funnel, and most of the blast will go right past him.
 * Subverted, in Tremors: Aftershocks, when Earl tosses a bomb in an attempt to kill a Shrieker, it lands
 * In Indiana Jones and the Kingdom of the Crystal Skull, Indy survives a nuke by hiding in a refrigerator.

Television

 * In the first season finale of The Walking Dead Dale and Andrea survive the explosion of the CDC by flattening themselves against a pile of sandbags.
 * In the Castle two-parter "Tick, Tick, Tick..." and "Boom!", Beckett survives her apartment being blown up by diving into her bathtub just as the bomb went off. More justified in this case since her tub is one of those old cast iron jobs.

Video Games

 * True of most "heavy" weapons in Mass Effect, including rocket launchers, anti-materiel rifles, and grenades: all of them are stopped by the flimsiest of cover. However, in Mass Effect 3, enemies have learned to throw grenades behind your cover—and you can return the favor by grabbing a heavy sniper rifle and sniping enemies through cover.
 * Against advanced Half Life 2 AI, the only thing you can do is hide.

Real Life

 * Nuclear blasts are strange things, sometimes a person can be vaporised while someone standing right next to them survives simply because of a wall.
 * During 9-11, a few survivors were found inside the debris pile. Most had been trapped in the bottom six floors of the stairwells, which had somehow remained partially intact.
 * Real bombs shockwaves are tricky things. Running down a side street won't save you if you are still within the danger area - the shockwave spreads out along any route offering least resistance. However when IRA terrorists bombed Manchester City centre, a traditional red telephone box suffered no damage apart from a cracked pane of glass, despite being well inside the cordon, and more extensive damage being wrought around it.