A $35 "teach yourself HTML in one week" book purchased and read cover to cover (in about 3 days) 20 years ago.

Round about 1998 I worked in software pre-sales, and visited ARM in Cambridge, UK to try to convince them to buy our software. They didn't. My bad. But the guy I met was so ecstatic that they had just had an IPO, I bought £3K's worth of ARM stock on the back of his infectious enthusiasm. Over the next few months they rose to ... £140K but my greed held no bounds and the inevitable happened as the dot com boom boomed. I got out at +£20K but still rue my poor decision making. Of course, had I held for the long term, I would have made a lot more.

edit: typo

Our house. We were in a position to buy during the crash (which was a little scary--I was working a temp job that ended the day we closed). Later we could refi the loan at 3.5%. Now about half the cost of renting in this neighborhood.

Nokia. Owned shares before the Microsoft purchase. Doubled my money.

I owned a substantial amount of AMD when it was around $2 a share. Sold when it was around $2.50. I think it's around $13 now...

US TIPS bonds at 7.5% interest that I got in 2000.

AAPL and FB.