Auggie says this to a Behemoth to protect an unconscious Luso in The Tainted Grimoire. He got interrupted by it's attack but succeeds anyway.
Inner Demons: When Rarity, Apple Bloom, and Spike are attempting to escape from the castle, they're confronted by Trixie, who attempts to take them back into custody. Rarity tells the others to run and holds off Trixie in an attempt to buy them time to escape, despite knowing full well that she can't take Trixie in a fight. Despite a power up from the Element of Generosity, Rarity is defeated and recaptured, but Spike and Apple Bloom escape.
During the Final Battle, the Royal Guard — led by Shining Armor and Cadence — fight any of Queen!Twilight's forces that make it out of the Gates of Tartarus, keeping them from attacking Ponyville.
Mimic's Dying Moment of Awesome in the Pony POV Series is built around this. During the "Origins" arc, it's shown that after Celestia and Luna first attempt to defeat Discord ended with him shattering the Rainbow of Light and killing Galaxia, Mimic held him off long enough for her daughters and their allies to escape. Naturally she dies, but in addition to ensuring their safety, she also becomes the first mortal to ever injure Discord in a fight.
The Dark World arc reveals that Queen Cadence'sLast Stand occurred when she decided to take on Discord and his enforcers — the Discorded Mane Six — all at once in order to buy time for her changeling subjects to escape. Like Mimic, this leads to her death, but she goes out with a bang.
The Hill Of Swords has Shirou pulling these a couple of times. First against the 70,000 strong army of Albion, then against Myoznitnirn, her army of Alvises and Jomungard.
Friendship Is Aura: When Lucario and Luna enter the underworld to rescue Celestia, the Mane Six use the Elements of Harmony to raise a barrier around the Gates to prevent any more of Tartarus' Mooks from being released to wreck havoc.
