In general, these threads are not ones necessarily created by any of the four Kanzenshuu staff members, but threads the community have unscientifically yet collectively agreed are important to understanding Dragon Ball, teach us all something new, or otherwise document something of historical value (likely in real-time).
WHAT YOU CAN DO
Do you feel there is a thread that fits this description? Something another community member has written that meets or exceeds the level of detail and scrutiny the Kanzenshuu staff would otherwise do themselves for the larger website as a whole? Respond with a link and your well-reasoned, well-written argument for its inclusion here!
As a general rule of thumb, please do not actually respond to any of these old threads linked below.
THE LIST
(in no particular order)

In "Dragon Ball's True Genre: We Need to Talk about Wuxia" (September 2015; creator: Kunzait_83), readers are led on a text- and image-rich tour of the wuxia genre, which undeniably shaped Dragon Ball beginning to end during its original serialization. Learn about the tales, stories, archetypes, tropes, and imagery that Toriyama (consciously or otherwise) directly pulled from to create Dragon Ball.

In "Better Sound Quality on Original Run of DBZ in Japan" (August 2009; creator: kei17), readers can see the beginnings of our community's discovery of higher-quality sound recordings for the series. In this more-recent thread, user/moderator Ajay sums things up a little more succinctly and with a bit more historical knowledge to reflect on since the original 2009 discoveries.

In "Color Correcting the Dragon Box - 3 Part Spectacular" (February 2012; creator: Ashura), readers are taken through the process of performing extra color correction and clean-up on the official Dragon Box DVD release of the franchise. Concepts such as color cast, scripting, artifacting, and more are broken down in detail.

In "Dragon Ball 3-in-1 Guide Thread" (December 2014; creator: eledoremassis02), readers can find detailed information about Viz's 2013-2016 "3-in-1" manga re-release, including censorship, misprints, and more.

In "Dragon Ball Z "Seasons" On Blu-ray: News & Discussion" (September 2013; creator: MagicBox), readers can re-live all of the announcements and hilarity of FUNimation's 2013-2014 Dragon Ball Z TV series release spanning nine "season" sets.

In "Jaco the Galactic Patrolman discussion" (June 2013; creator: Wobbuffet), readers can re-live the announcement of and not-so-secrecy behind 2013's Jaco the Galactic Patrolman, an all-new prequel to the Dragon Ball franchise by original author Akira Toriyama himself. Also, "Dragon Ball Minus" got shoved in there at some point.

In "Official On-Going DBZ 2013 Movie Thread: 'Battle of Gods'" (July 2012; creator: JulieYBM ), readers can re-live the (pre-)announcement through international release of the first theatrical Dragon Ball film in seventeen years.

In "Official On-Going DBZ 2015 Movie Thread: "Resurrection 'F'" (July 2014; creator: JulieYBM ), readers can re-live the (pre-)announcement through international release of the next modern-era theatrical Dragon Ball film.

In "Ocean Studios' "Dragon Ball Kai" dub" (September 2010; creator: JulieYBM ), readers can learn all about the vaporware Ocean Studios dub of Dragon Ball Kai (from the original leaks to deleted announcements and everything in between), which is confirmed to not only exist but essentially be complete, yet will seemingly never see the light of day.