"Hell Yes!" Moment

The moment at which a character realizes that things are finally starting to go their way when they're in danger. Perhaps it seemed that the only option was a One-Way Trip or a Heroic Sacrifice, but suddenly The Cavalry appears on the horizon. They might not say anything in particular, but the look on their face is priceless.

The effectiveness of this moment can be affected by their change in confidence. An arrogant, so far unbeatable supervillain suddenly realizing he's got the ace in the hole he'd been hoping for is difficult to make this trope work with, but a downtrodden hero or Ineffectual Sympathetic Villain who has faced hellish adversity at every turn can usually pull it off with little difficulty.

Basically the Inverted Trope of Oh Crap. It can often be an Oh Crap moment for the opponents of the character having a "Hell Yes!" Moment.

Some situations where this commonly occurs:
 * Just in Time
 * Big Damn Heroes
 * Changed My Mind, Kid
 * Conveniently-Timed Attack From Behind
 * Deus Ex Machina Airlines
 * Forgotten Superweapon
 * Gunship Rescue
 * I Got You Covered
 * Let's Get Dangerous
 * Misfit Mobilization Moment
 * Villainous Rescue

Not to be confused with Big Yes, And the Fandom Rejoiced or Crowning Moment of Awesome, although a "Hell Yes!" Moment can and often does precede the latter. Do not be surprised if the series theme song begins to play.

When this is subverted, it is a Hope Spot.

Anime

 * In Tengen Toppa Gurren Lagann, Nia have this reaction when she realizes her ring is glowing.
 * Much earlier in the series, Rossiu has one as Simon shows up for his epic He's Back moment.

Film

 * A character has this reaction in Friday the 13th (film) when he sees the upgraded android KM-14 about to fight Jason Voorhees.
 * Lord of the Rings: Plenty of them. When Gandalf and Eomer arrive at Helm's deep, both Aragorn and Theoden make those. When The Rohirrim arrive on the Pelennor fields, Gandalf makes it. When Sauron explodes, All the fellowship makes it.
 * The ending of Ink gets two of these: when Ink  and when.
 * In Last Action Hero, Danny has one of these when Whitney escapes her captors and pulls a gun on the guys holding him. Everyone notices.

Literature
"Marco: 
 * This happens in Animorphs #45, when Marco is fighting aliens who look like a cross between Cthulhu and razor blades, giving us this priceless quote:

Marco (Narrating): They had exactly one second to think I was insane. Gigantic paws, armed with claws that can gut a salmon before you could say "lox" knocked their heads together."


 * Rachel then proceeds to Curb Stomp the Hork-Bajir.
 * In Owl Knight of The Heralds of Valdemar, Darian and his companions are up against a snow-drake when heading northwest to find his parents. Things seem impossible, until Healer Keisha fires an arrow hitting it at the right spot. To Darian's amazement, Keisha runs right up to face the snow-drake, followed by younger sister Herald Shandi who shouts the Trope expression.
 * In With a Bullet, the third Shadow of the Templar novel, Mike has this reaction when Johnny shows up in a glorious Dynamic Entry/Big Damn Heroes moment.

Live Action TV

 * In the Babylon 5 episode "Severed Dreams": as seen here, after multiple Oh Crap moments, the bridge crew collapses in relief when they realize the third assault force attacking them is actually on their side.

Video Games
"Deadly: Outlaw, this is Deadly, refit and fully loaded. You guys miss me? Marine: HELL YEAH!"
 * In Batman: Arkham Asylum, a hostage of one of The Joker's thugs has this reaction when he sees Batman sneaking up behind the thug.
 * At one point in Call of Duty 4: Modern Warfare, after the player's squad links up with another one trapped behind enemy lines, a trio of enemy helicopters show up to drop more troops. Then Deadly comes back and shoots them all down.

Western Animation
"Magneto: Did you think I would let you die alone, Xavier?""
 * The first season finale of X Men the Animated Series had this with the team fighting a losing battle against "THOUSANDS of Sentinels!", and Professor Xavier's jet crashing to what looked like a fiery death...only to stop falling a foot above the ground and be righted by a magnetic field.


 * In the Grand Finale of Teen Titans, after Beast Boy and his Ragtag Bunch of Misfits have all been captured, almost a dozen other Titans we thought were captured suddenly burst in. Cue Crowning Moment of Awesome for the entire show.