I’ll start…there are a few…I should preface this by saying I don’t buy and sell stocks myself.
When electronic medical records were a new thing, our doctor friend mentioned this one to us. We should have listened…but didn’t.
I wish I had bought stock in Zoom in January 2020.
Chipotle and Priceline.
I used to eat at Chipotle in Torrance, near Los Angeles, when it was owned by Mickey Ds. We’d go 3 days a week. Like early 2000s
And Priceline - when you could bid on rooms, I always did.
And made out like a bandit !!
Buy what you love.
I did watch the Chipotle IPO but it jumped up very quickly. Should have bought. Priceline, now booking.com, was one of the top performers in a 20 year period.
I own some good ones (and dogs). But not that good !!
I don’t buy individual stocks. I primarily buy index funds. That said, I used to own a small Internet company that had a good amount of international revenue. One of the largest sources of annual revenue suggested paying me in Bitcoin due to easier international banking + tax benefits. I refused the offer and insisted that they instead use what I considered at the time a more established payment method.
This occurred back in early 2010s, when Bitcoin was worth a minuscule fraction of current value. Had I accepted their offer to be paid in Bitcoin and I held on to it (there is a good chance I would have held the bulk of the sum), the payments would be worth something on the order of $100 million today.
Oh my on Bitcoin! Still not sure I fully understand what that’s all about so would have turned that down as well.
We have bought and sold individual stocks for over 30 years. Also have plenty invested in various funds, etc. but both DH and I like following the market and have a decent appetite for risk. Our first purchase was a product we really liked and used so when it went public we thought why not- it split a couple times and we tripled our $ so we sold it.
Have we had some dogs? Yes, a few. We’ve had far more winners and some that have done exceptionally well. I can’t really say there was anything I wished we had bought but I know my DH has a few.
My problem is not what I didn’t buy, but what I sold too quickly. I like to make my quick little profit and usually buy good stocks, but when they jump, I sell. And they keep going up.
Buying individual stocks on the retail market is much more akin to speculating than investing. Sometimes the next big thing really is, but more often than not, it isn’t. So, why look back with regret? Conversely, don’t be too confident if you lucked into a winner. 
My dad always says - better you make some money than none.
It is painful - what you describe - but you have to look at the bright side.
Hindsight is always 20/20!
Back in the early/mid '90’s I worked in a building that also housed an early tech start up. A guy in my office always said we should invest in them, but we never did (nor did he). A few years later they were acquired by AOL.
Shoulda,coulda woulda
Concur Technologies. Was down to ~$1 a share and ADP bought them for something like $70-75 eventually. Implemented the software at a company and just knew it would be successful.
Amazon around '14-'15. Worked at a company that sold product to Amazon. Just knew they would become the next big thing in retail to start to rival Walmart. Both companies treat their suppliers like cr@p. Fun fact back in the 80s when long distance was a thing Walmart purchasing department would call their suppliers collect. Orders straight from Sam Walton. Amazon on the other hand if they make a mistake receiving your product they will just short pay the invoice. Then make you jump through hoops to get your money. Also Amazon will fine you at the drop of a hat if you are a supplier.
Amazon and Google. I’ve worked in tech companies so we had good internet access before that was a thing for most people. I started ordering books on Amazon pretty much when they opened the doors because just about any book you could think of would show up in the mail in a few days. They even used to send small gifts to customers around the holidays! And Google was miles ahead of the other search engines at a time; I remember showing friends who hadn’t heard of it how great it was.
But when these companies went public there was a flurry of interest and I sure wasn’t going to pay those inflated prices for their stock! Also I was reluctant to buy individual stocks instead of broad mutual funds so I never did buy shares.
Since IPO Google is up about 200x and $1,000 invested in Amazon when it went public would be worth over $2 million today
Yeah but the normal everyday investor never gets the IPO price.
For these two stocks, in the mentioned timeframe, the difference between the IPO price and the prices on the first day of trading is purely insignificant noise.
This is true years later - but on that first day when something is up 50% of 100%, you get nearvous / weary. That’s why I didn’t buy Chipotle.
On the flipside, Charles Schwab and Ameritrade used to give out IPOs. I didn’t get Facebook but my sister did and it went down half or near half from the IPO price.
If only I bought in…
But…no one knows.
You do the best you can and hopefully at least keep ahead of CDs, etc.
The smartest investing, of course, is through your 401K with a match - and dollar cost averaging. It’s boring but smart.
But the poster said specifically between the IPO and today
The thread is all about hindsight 
Yes, it’s an odd thread in that - every stock that’s had an IPO and gone up - is one I wish I owned.
My daughter, in college, just starting at - bought Cava several months back at 45 or 49.
It’d had an IPO and went up and I was like - it’s too rich - and sure enough it went down into the high 30s if I recall.
Now it’s $95.
And like any good, in hindsight investor, she says, I wish I didn’t buy just two shares!!
Of course, with no commission, you can do that today. Heck you can buy fractional shares.
I sure wish I bought even 100 at $45 like her.
Maybe I should add that to the list.
And TSLA a month ago.
But any stock that has gone up - of course, you wish you bought that!!
But the thread is not about random stocks or stuff that went up in value over a random period of time. It is about stuff or stocks or whatever posters considered but for some reason didn’t buy. 
The Dot Com bust of 2000 left tech stocks at a discount. I believe Amazon was $6 a share then. I wish I had a crystal ball.
Not stocks… but something that definitely appreciated in value since I first considered it. I should have bought that Reissue back in 2009! I don’t think I can plop that much $$ on it today. Ditto a Catogram Neverful in 2018 (?) Can’t imagine paying the resale price!
Yes I addressed in the first. Chipotle and Priceline.