I could rattle off a two page report on the following without touching a book or Wikipedia:
Abraham Lincoln
Henry the Eighth
Al Capone
How about you?
Does it have to be factual?
Guess.
How to write and submit a picture book.
Ditto for a story for a children’s magazine.
I have to do it all the time at work but it is more like 10 - 20 pages. Unfortunately, they are all about obscure systems in the medical devices industry that compliance people check for formatting and terminology, file away and nobody ever reads again. Think TPS reports.
I can easily write a 2 page essay on lots of neuroscience, computing and aeronautics topics off the top of my head. Also include Louisiana history and culture.
Seriously, I could knock off 1,000 words or so on my college major and on a couple of industries I consulted for before I retired. I can’t guarantee the information would be the most up to date, but what I would write would be accurate, and would be written plainly enough for the general public.
The French and Indian War in general and most battles and personalities involved.
Some firearms and aspects of gunsmithing.
Russian coins and paper money up to 1917; all money during the colonial era 1600-1800.
Motorcycles; their care, use and history.
Most amusement parks east of the Mississippi.
Dog training
Migraines
Autism
Napoleonic wars, particularly from the British perspective
Urban fantasy, science fiction
Things That Piss Me Off
Property Insurance
Air Traffic Control
Woodworking
I was hoping to see more threads here on neuroscience when I joined. Most of them tend to fall flat pretty quickly. Not sure why I am fascinated with it.
Installation, maintenance, trouble shooting and repair of fire alarm systems.
Hey, longhair75! Yes, I know you could. But you probably wouldn’t even get to smoke detector placement on sloped ceilings with beams. 
True. Also, smoke detector placement for smoke control for fire doors. Or ground fault diagnostics , locating and repair.
As an EST dealer, I could do a few pages on how to write programming rules for the EST 3 system. I am also maybe one of the last IRC 3 programmers left in the business
Lord Horatio Nelson
machine learning
web development
interpretation of Moby Dick
The Wars of the Roses
The Princes in the Tower
The Rules of Hockey
The Battle of Verdun
Standard manuscript format
Cooking eggs
History of pie throwing in movies
Traffic (the rock group)
Many more.
My kids would argue that I only speak in 2-page structured reports 
Many topics. My area of expertise includes developing structured arguments on the fly so I bring that to any topic.
However, within the context of the SDMB, would y’all be surprised if I went on for a couple of pages about guitars?
Um, sex.
The past fifty years in music.
Anything to do with the 1960’s
Anything to do with real estate
Musical theatre
The Legion of Super-Heroes
Serial killers
Isokinetic source sampling for air pollutants
Basic weather understanding… how the atmosphere behaves
Motorcycle operation and handling
Single-engine airplane operations
Traffic dynamics and survival (not rock groups :))
Backpacking/Camping/Hiking
North Carolina topography and ecosystems
Combustion engines; compare and contrast