Bitcoin. I knew about it from the very beginning.
Now, I half have a large regret and half tell myself that I would have lost it all anyway.
At some point in the next year or two, up to 90% of that will be returned to the 25,000 creditors who filled in the paperwork to make a claim years ago.
Did keep a couple as a hedge fortunately.
I console myself in the fact that I would have sold any Bitcoin I might have mined well before the price really took off.