Stunt Bonus
A character can stunt any action that requires a d20-based roll (such as an attack roll, ability check, skill check or saving throw) gaining a stunt bonus to that action based on the description of the action. This bonus may be applied to a d20-based roll that is part of the action or to a related static value such as AC. If applied to a static value, the bonus lasts until the start of the character's next turn, otherwise the bonus lasts for the duration of that roll it is applied to.
Note: Despite the name, stunting does not always involve high action and over the top dramatics that have escaped from a martial arts movie. Stunt bonuses can equally be gained from adding colour to a scene, demonstrating character quirks or personal drama, tying in a character's background or anything that adds to a scene and makes it more enjoyable for everyone.
Be careful when using stunts, however. Try not to get long-winded or overly tied up in your idea of what’s cool. The point of stunts is to make the game more fun, not turn it into an interminable blow-for-blow description of a character’s every eye twitch. Brevity is key. Keep stunts short and relatively simple.

+1 Stunt
The most basic stunt adds a bit of colour to the game, filling out the scene for everyone, or simply provides a good description of an action. A +1 stunt also broadens the definition of what is possible just a bit, allowing a character to perform feats that border on the impossible (running up a wall to flip over someone, sprinting through an angry crowd without slowing down, cutting an arrow out of the air etc.)

Examples
    Dane draws his sword and flourishes the blade. Eyes narrowed and fixed on his foe, he readies himself to cross swords once more.
    Adariel drops the musty old book on the table with a loud thump, then adjusts his glasses as it falls open to a very interesting page.

+3 Stunt
These stunts not only do have to have an engaging and fun description, but also interact with the setting in a relevant way. This can be a fun use of the physical scenery or the utilization of setting or character details to bring everyone deeper into the game. A +3 stunt pushes the realms of possibility further than a basic +1 stunt, enabling nigh impossible feats (running up the side of a collapsing tower, catching arrows out of the air, stunning an entire room into silence with just a look etc).
Examples
    Ara hefts her shining golden sword and leaps toward the Prince, revealed to be a thrall of the red dragon. At the apex of her arc, the blade scythes through the prince's statue, sending the head flying even as Ara’s sword hurtles toward the man himself.
    Opening the ancient tome as the demon bears down on him, Adariel begins to utter an incantation of binding. "This is the tome that allowed you into this world. It is fitting that it shall drive you from it."

+5 Stunt
+5 stunts are indefinable. There’s only this guideline: If everyone at the table sits up and says, “Wow,” that’s a +5 stunt.
If any doubt exists as to whether a stunt merits a +5 bonus, it isn't a +5 stunt.
These stunts are the ones that are such spectacular ideas or such perfect descriptions that everyone thinks they’re awesome. Or at least the Storyteller does.

Examples
There’s no example for such a stunt here. These really depend on the individual game and on the people playing it.