I regret not taking my brother up on his offer to buy Bitcoin, just for the laughs, back when it was just starting. His friend offered to a few dollars worth of bitcoin back in the day, and I'd thought the guy was nuts for offering. My brother decided to humor him, but I hadn't the money to just casually throw into the pot. I was just a student back then, after all.
Man, that five dollars' worth of Bitcoin would have ballooned in value by now.