The husband/wife team of Duke James of Krondor (aka Jimmy The Hand) and the telepath Gamina blowing up the whole city of Krondor using medieval technology to destroy an enemy army. This is arguably the greatest Heroic Sacrifice in all of High Fantasy. And the best part? They didn't feel a thing as their bodies died, as Gamina used her powers to overwhelm both their senses with memories of every joyful moment they had together over 40 years of marriage.
The Krondor maneuver was based on an earlier tactic by Guy du Bas-Tyra, who ignited the naphtha mines beneath Armengar after luring in a significant part of the moredhel armies.
Pug dropping the Kelewan moon onto Kelewan to stop a Dreadlord from emerging into the First Plane. Even Banath was impressed by that.
Not to mention how Nakor lured Leso Varen to him and permanently killed him, something that Pug couldn't accomplish in the century or so since their first encounter.
Amos Trask getting through the Straits of Darkness when it was almost winter, something very few sailors, if any of all have accomplished.
Martin disabling a tiller in Magician on a ship that was chasing them from a distance when escaping from Krondor.
Another one for Jimmy/James. Setting up a intelligence agency for the entire Kingdom and having spies everywhere except for Queg. This lasts until the Chaosaga, the final arc of the series. At least a century after he died.
Nakor's tricking the Panathians into burning the ship manufacturing factories down. Also doubles as a Crowning Momentof Funny.
Anytime Pug puts Patrick in his place in the Serpent War Saga.
The ending for Magician's End. Yes, Pug and Tomas are dead, but the Dread have been stopped and peace has returned to Midkemia for who knows how long and Magnus still lives on, so Midkemia will always be safe.