Wow...Over this Campaign, only 2 stand out.

1) vs. Iron Warriors: Cleanse Mission. The Blood Angels, beaten, and thoroughly outnumbered, thanks to the Defiler's and Obliterator's fire, decimating the Panzer Units. The Librarian Charged into the lines, and summoned The Grey Knights thansk to the Homer he has as a bookmark! Tied them up to the last turn, causing a draw.

2) vs. Tyranids: Skirmish. Sang High Priest proved that having him with Lightning Claws makes more sense than a Librarian with Lightning Claws. Cuts down the Hive Tyrant in one round of combat, and was on the way to remove the Carnie at the end of the game.

Those are the only two that most recently stick out in my mind.
Brother Captain Cameron Davion, Leader of the Sword of Sanguinius