As you probablly already guessed it was another copy of Superman's debut in Action Comics issue #1
The price $1,500,000
Though I was not alive in 1938, pardon me while I take a break and kick myself in the ass for all the ones that I did throw out.
No, I never had that particular issue but certainly had mountains of others that too were valuable.

I know there are plenty of other old timers in our club that have these same feelings