Most Dramatic Return In the Middle of Battle: For Great Justice!

[krugaan]

The scenario:

party of barbarian, bard, paladin, wizard facing down hordes of undead led by a lich. As the ghasts and zombies shamble closer to our heroes, whose resources are slowly dwindling, the bard says, "Well guys, looks like this is it. If only Thorin were here..."

And then ... from the darkness ... "Ask and ye shall receive, Gregory! TURN UNDEAD!" Dozens of ghasts turn and flee while scores of zombies simply crumble to the ground as a stout figure holding a radiant shield aloft advances.

"THORIN!11!!one!"

Now... the question is this...

What other enemies / returning hero-saves-the-day combinations are there, chosen for ultimate awesomeness? (The previous example was hordes of undead / cleric.) Basically, im looking for encounters where one class, skill, or power can turn the tide of battle in a suitably dramatic way.

For example, a ranged sharpshooter fighter against a beholder: relatively unhindered by the anti-magic properties of the central eye and able to hit the beholder with large amounts of burst damage from any position.

Any others?

Remember ... MAXIMUM DRAMA.

[Madbox]

Rogue, wizard, and bard. They have been fighting a long slog against hordes of goblins, and were winning. Then, out of nowhere, a Troll appears! BAM! The wizard is KO'd in one hit! The bard is out of spell slots, so no healing, no acid, no fire! BAM! BAM! Rogue is almost unconscious!

"Man, I can't leave you guys alone for five minutes, can I?"

The fighter, the party tank, arrives with torch in hand! SIZZLE! He distracts the troll with a lunge from the torch, scorching its flesh! Rogue goes for the sneak attack and disengages! Bard does a medicine check, the wizard is stabilized! Troll fails to regenerate, and goes after the one with the thrice-accursed flames. BAM! "Is that all you got?" the fighter laughs, shrugging off the bone-crushing blow. He swings the torch, burning the troll once more. Rogue sneak attacks again! The troll looks weak on its legs! TWING! THUD! Bard shoots the troll in the head with his crossbow, finally taking down the threat.

Sometimes, you really just need a tank to absorb hits with their face.