That it made it so easy to whip up UIs and access Windows APIs, having never done it before as a 10-11 year old playing with VB6...

...which I think promptly used as a younger teen to write a custom keylogger for a friend to try and steal RuneScape accounts. Good news is I didn't know how to send emails from it, so even though it worked, it couldn't hurt anyone in the end!

It taught me what "double buffering" was, because I was (ab)using it to try and build games, but didn't understand why I was getting this horrible white flash when I cleared everything!

I learned so much with VB6 haha