I'm starting with the assumption that #1 on that list is "what's the best chain lube" so we'll start with #2. My guesses would include:
-- How many rear gears do I need?
-- Drop bars or flat bars?
-- 1x, double, or triple crank?
-- Sunscreen or SPF clothing?
-- Best place to ride a bike?
-- Take the lane or stay on a bike path?
Feel free to add your favorite bike-related thing to argue about.

And then, for bonus points, consider the following:
What do respondents to this topic need to know about the questioner's circumstances to have a reasonable discussion, rather than polling who can shout the loudest and / or longest?
Are there any arguments against your favorite answer that have some merit?
And for double bonus points, why do you care what other people think about this/these topic(s)? (with apologies to Richard Feynman)

Do you wave at other riders?

The wonder is everyone doesn't get bored with it

Shimano or Campagnolo.

Obviously.

Biggest waste of money?

....clipless vs platform pedals
....do you buy coffee, donuts and beer for your LBS and do you tip bike shop employees
....cable discs vs hydro discs
....proper length and color for cycling socks
....back pack vs panniers
....rolling resistance of tires
....chain lube threads
....best frame material

Pretty much anything posted in General.

If you find our General Discussion upsetting, don't go to MTBR

Where do I buy a fast/ light/ reliable/ long lasting bike for $500???

Craigslist!

Meta threads about other threads.

Anything in the vein of asking if a taco shape wheel can be fixed or how to make cog spacers from paper just need merged into a single post and moved to the bowels of the forum.

the more divisive ones to me seem to be the "new" vs "old" type, even if the things aren't actually newer or older, but just seem like it.

mechanical or electronic shifting
tubes or tubeless
bike computer or smartphone
pump or co2

Seat post min insertion marks.

Has MTBR gone down the pan? It used to be really good around 15-20 years ago when I was following it actively.

Threads about needless most contentious topics...LOL!!

"Riders of that-other-style-of bikes are doing it all wrong"

Or, alternatively:

"Tell me about how you all do such-and-such, and I'll tell you how you're all doing it wrong!"

I'll take contentious over garbage. All the "Do you..." threads with no purpose other than for the OP to see his name in print. Look at me, Mommy.

I'm a roadie - and I use a camelback - so nanner nanner.

Can we talk reasonably about why helmet use increases the number (not severity) of accidents?
hehehe

Those cheap frames and aftermarket products (from you know where) are a mortal threat to everyone riding bicycles.

Why aren't you cyclists riding puncture proof (solid, or foam, or metal matrix) - tires?

Not a fast learner, but learn me to go fast - on my used and rusty Wallymart Wonder - that I'm trying to make fit.

Best saddle?

Does crabon fibre azzsplode? Will my plastic bike melt?

My heavy (40 pound) bike gives me a better workout!
My heavy (19 pound) bike gives me a better workout!
My lightweight (11 pound) bike gives me a better workout!

Spring is almost here...

How many more posts before we have a full list of every possible topic concerning bicycles?

Mostly it's fine. The algorithm that feeds threads to the splash page makes general discussion a dumpster fire. At first after the software update it was also feeding in "off topic" and it was really bad. To their credit they fixed that

No list is complete without mentioning this:

-- rotating mass

Any thread that has the word "best" in the title.