Ensemble Darkhorse: Panamon Creel is a very popular character, for his morally ambiguous nature, general badassery, and dramatic flair. This led to both the creation of Padishar Creel in The Heritage of Shannara, and Panamon's starring role in the short story The Black Irix.
Fridge Brilliance: Panamon Creel mentions that Paranor is haunted when Shea brings up that he wants to go there. After reading other Shannara works like The Dark Legacy Of Shannara and the graphic novel Dark Wraith of Shannara, Panamon's talk makes sense; magic protects Paranor and attacks any intruders trying to break in. That's what probably gave rise to the in-universe beliefs that Paranor is haunted.
Ho Yay: Menion Leah is very obviously head-over-heels in love with Shea Ohmsford. Which, when you think about it, might explain why Shea's older brother Flick dislikes Menion so much.
One-Scene Wonder: The Warlock Lord, in Sword and High Druid. He gets a little more screen time in First King.
Seinfeld Is Unfunny: Nearly 40 years ago, when the fantasy industry was in its infancy, The Sword Of Shannara was hailed as a worthy successor to Tolkien's epic. Now the prevalence of the tropes in it can make it seem rather cliché.
The Elfstones Of Shannara
Fridge Logic: Allanon didn't need Wil at all, only the Elfstones. True, the stones can only work for someone to whom they'd been freely given, but since Allanon was the one who gave them to Shea in the first place, and from Shea to Wil, why couldn't Wil just give them to Allanon and then have him present them to any fullblooded elf who could use them safely and leave Wil to continue his studies?
Growing the Beard: As mentioned on the main page, Elfstones is often seen as the point when the series as a whole grew the beard.
Harsher in Hindsight: The Federation refuses to help the Elves and their allies in the War of the Forbidding as they are skeptical of the Demons in the first place and said Demons haven't directly attacked them. It turns out in the later entry, The Dark Legacy Of Shannara, that the Demons escape the Forbidding again, this time turning up in Federation territory. They raze the Federation capital, killing its defenders and much of the populace.
Nightmare Fuel: While many of Demons could be this, by far the biggest source is The Reaper.
Ensemble Darkhorse: Garet Jax, the Weapons Master is one of the most consistently asked about characters in the series, due his mysterious air and incredible fighting skills. He now has his own short story, The Weapon Master's Choice, which explores who he was before the events of the story.
Tear Jerker: This is the one where Allanon dies. And then there's Jair's companions. Helt's is particularly poignant, as is Garet Jax's. In a nondeath related example, Slanter's goodbye to Jair is also quite touching.