At around 12 years (having learned some extremely basic Q-BASIC from a book, no computer at home to test it on) I co-wrote a scareware with a friend from school on their family computer. It would fake formatting your computer. We knew about GOTO, but not about loops (or faking them with GOTO). So we copy and pasted the same line 100 times and edited the number in every line :D Good times ;)
10 PRINT "John is AWESOME
20 GOTO 10
..and little 10 year old me discovering how to BE GOD BY HARNESSING THE POWER OF INFINITY in your computer.