It’s called correction tape. I don’t let myself use them because I’ll just doodle lines on paper and run it dry.
I like the Pilot Dr. Grip pens. The one I linked is the one I use; it says the grip is navy, but it’s totally purple. 
It’s nice and heavy. I hide it when I’m away from my desk so no one will swipe it.
My pencils are Ticonderoga #2. World’s Best Pencil, it says so right on the box!
I work for a Japanese company, erasable pens are a thing and they stock them. I love being able to use a pen and erase my mistakes instead of scratching them out.
If I had to pick one, Post-Its. We go through those things like we’re Rube Sofer.
I love binder clips because they are so versatile. Like others I use them in my kitchen to seal freezer bags, bags of chips, bags of croutons, and bags of… well, basically any and all bags (clothespins work good too on smaller bags). They’re also useful as mini-clamps when doing electrical work or similar things where semi-precision is needed.
I also love gel pens, even preferring them to my beloved fountain pen. EnerGel and Pilot G2 are faves, 0.5mm of course.
Good ‘ol fashioned 3-ring binders are a godsend for organizing lesson plans, syllabi, and copies of worksheets, handouts, and paper assessments.
However, my single favorite office product is the Xerox machine. I can make do without a lot of stuff: there’s always cheap Bic pens available if my gel pen is depleted of ink, paper clips of all sizes when I run out of binder clips, good ‘ol Ticonderoga #2’s and the wall-mounted sharpener for when my mechanical pencils run out of lead, and scraps of paper and scotch tape available if and when I run out of Post-Its.
But if my copy machine dies I’m well and truly fucked. I literally could not do my job without a fast, dependable copy machine. Having integrated hole-punching and stapling ability is nice but not required.
Yaaaaaassss!!! The first time I used it, it was like the heavens opened up and a choir sang. I hated the old- school white-out in a little bottle with a brush. A thin layer was transparent; a thick enough layer never fully dried. I am certain that if you dug up my sixth grade homework and tried to write over those lumpy white bubbles now, they would still burst and ooze like a new pimple.
I love my 4-color pen. It was my briefing pen in law school; I underlined facts in green, issue/holding in red, black letter law in black, and dicta and concurring or dissenting opinions in blue. Many of my friends had complicated systems with 7 different highlighters, but I could easily work at the beach with my single perfect writing implement. I still use it to this day; one lives in my purse at all times.
This !
Good for crossword mistakes.
My Pentel Graphgear 500 in .7mm, best inexpensive pencil I’ve used. For pens, my Pilot Precise V5 in Extra Fine, colors blue, red, green, & black, handy for checking drawings.
Another vote for the Pilot G-2.
I was a professional Digital Computer Operator in the 1970s, back in the days of big mainframe installations. New tapes came with rings, which we usually left in, but we had piles of them laying all around. There were also moveable posts around the computer room for stringing cordons around, which were only used for special occasions like Family Open House Day. Otherwise, we all sat around playing ring-toss trying to toss the rings onto those posts.
Nobody said “red, Swingline stapler” yet? 
This item probably changes every day for me because there are so many clever office supplies. I like cool magnets, post-its, neon papers, and everything else.
Today, I’ll go with something that is becoming very hard to find. The Reporter’s Notepad. It is tall, narrow, and spiral bound at the top. It is usually narrow ruled or college ruled. It fits perfectly when you have little to no desk space but still need to make notes for yourself. I use them in meetings when I am the person presenting. That way I can make quick notes and not have it mess up (or slow down) whatever presentation I am sharing with the team. This is important as sometimes I am critiquing my audience and don’t want to accidently reveal what I am up to.
While I love my G-2 (10), my vote goes to the SortKwik fingertip moistener that I can’t live without. My job involves handling an obscene amount of physical paperwork. The SortKwik gives my hands just the right amount of stick.
Binder clips are awfully nice but I have to give the win to Sharpie pens. Oh man, I love Sharpies, they write on anything and it stays there. They’re #1 on the “borrow” list though so I guard them jealously.
I do the same thing, plus I have a slightly smaller than a ping pong ball sized neodymium magnet stuck to my fridge that I keep all binder clips on.
I love those staple-less “staplers”. Hurts like Hell when I’m going through files and a regular staple cuts between the fingernail and the finger, or makes a deep cut on the fingertip. I avoid it by using the little device that attaches the sheets of paper using said sheets of paper. Whoever invented the thing was a genius!
So, Sharpies. I read somewhere about this dude who absotively hated some guy he worked with. They used Sharpies doing their job, so this dude bought a dozen and removed all the caps, then let them sit around and dry up.
He then surreptitiously replaced hated-guy’s Sharpie with a dried out one. He could see his desk from where he sat, so he saw him go to use his Sharpie and it was dead. So, guy got a brand new Sharpie out of his desk and got back to work.
Of course, next time hated-guy went to the men’s, there was another substitution. And this went on for months, with varying time between new Sharpie being opened up and dry Sharpie replacing it.
I call those the “IT lockpick”. I am constantly ruining paperclips at work to reset devices or pop out SIM cards.
My personal favorite is a staple remover. I don’t use them very often, but they are really fun to fiddle around with on a long phone call. The person calling me can’t see my savage staple remover attacking everything else in my office with its metal fangs.
Now I really want one that looks like this:
Well, it is definitely one of my most prized possessions, and I was about to mention it, but I couldn’t in good conscience single it out among various other office supplies. I probably should have.
I still have – and regularly use – a red Swingline Tot 50 stapler that I have had since I myself was a tot. (Still in good operational condition too, tyvm.)
An employee at one of the big-box office supply stores told me several years ago that ACCO would soon discontinue making those miniature staples for it. So I immediately bought a couple of boxes of them, which I think should last me for the rest of my life.
Pro tip: When you find a product you like, buy a lifetime supply because they will quit making it.
(And I still have a Royal Portable typewriter that I got for my Bar Mitzvah, circa 1964, back in the day when they were made out of metal instead of cheap-ass plastic. This, however, I haven’t used for umpty-ump years and I haven’t even investigated whether I can still get ribbons for it.)
Do you know who ELSE loves Sharpies?
That guy was a savage genius!
Nooo… but tell me so I can hide mine if he’s ever in the neighborhood!