The Red Hand of Doom (wikipedia entry) by Richard Baker is a 3rd Edition Dungeons and Dragons mega-adventure. When it was released, I remember reading about it and thinking “This sounds very close to the H-Series Bloodstone Pass Saga, so I'm going to get it and run it.” And I'm thankful that I did.
What made this unique was the excellent character interaction. There was Averron, the ranger who was seeking vengeance on the warlord of the Red Hand armies. Slade, a male bounty hunter on the cold trail of a woman who had escaped. Aversanno, an elven wizard archer who, along with his diabolic familiar, was hungry for power. Gabe, the austere halfing druid who was tasked with protecting Glib, his younger brother. Glib was a carefree halfing freak-show (bard / cleric aspiring to be a geomancer).
The campaign started in the hearth of Glib and Gabe's parents inn. They needed to investigate some marauders. It was here that the heroes stumbled into a greater story. The hobgoblins of the mountains were hiring mercenary ogres to join their ranks and crush the Elsir Vale. Glib and Gabe's mother insisted that they all needed to warn the Elsir Vale. The parting conversation between Gabe and his mother was “Watch out for your brother. If anything happens to him, I won't forgive you. Now take this healing potion. It is for Glib's use only. But you should keep it safe.”
The party traveled south to the Elsir Vale, and had several memorable encounters: a sneaky hydra, an assault on a fortress, defending a village from a raider attack, and a handful of truly memorable battles with dragons.
The first dragon encounter was well planned, but poorly executed. They had protection spells and buffs going, but didn't know that the dragon could move so fast. It almost ended in a complete loss, but thankfully they were able to retreat.
The second dragon encounter, much later, was memorable as it was a multi-tiered battle with different fronts to defend and hold. The combat remains an all-time favorite:
During the combat, as Slade and Aversanno gave chase to a severely wounded dragon, leaving Averron, Gabe and Glib alone. While cleaning up the minions, Averron was charmed by a hidden foe. Averron, with a look of sorrow, chopped into his dear friend Gabe, slaying him and rather remorsefully dumping his body in a watery grave. The hidden foe, using a disguise spell, then appeared as Gabe and told Averron to go after Glib. Glib was able to shake Averron from his charm, and they turned to defeat the imposter.
During each of these combats, Slade, would always enter his barbarian rage with a high pitched scream; You see, Slade was in fact the woman which “he” was trying to find. Slade figured the best way to find her daughter was to track the people looking for her. But the attention to detail was great. At every point, Matt made sure to leave clues about Slade's nature.
Gabe and Glib interacted as an responsible / irresponsible brotherly pair. Gabe was always keeping a watchful eye on Glib, who's antics and direction were chaotic. Glib was carefree, while Gabe was world weary, and struggled with his family relationships.
Aversanno, with promises of power from his wicked familiar, eventually sold his soul for even greater power. The familiar's influence didn't stop there; Knowing that Averron was seeking vengeance, the familiar offered power to Averron for his soul. Averron accepted.
Sadly, due to two players moving away, the campaign collapsed. For awhile, when one of the players moved, we used RPTool's Maptool and Skype to facilitate gaming. It worked reasonably well to have one remote player and all the rest gathered round a table; But the constraints of the tools and the lack of face to face interaction greatly reduced the feel of the game. With a second player moving away, the game was scuttled.