I have an awesome story that i think I've told before, but I'll tell it again anyway :)
My father-in-law is a pharmasist. back in the early 90s computers were starting to make their way into Pharmacy and the first few pharmacy sortware packages appeared. this increased with time, as you'd expect. At some point he decided it was inevitible but he decided (I have no idea why, except that he's always been quite independent) he'd write his own software. Took himself off to nightschool and learned dBase III. He'd never written a line of code prior to this.
He then proceeded to write an entire pharmacy suite of software tools that are still in use. They've been heavily updated and added to over the last 20 years but it's still all DBase III running on DOS. It's a saggering amount of code over hundreds of files but it all works. I've seen the code and it wouldn't pass a first semester coding course. each programme is a single 10,000 line spaghetti-fest. I've tried to explain functions/methods to him but he didn't understand and in the end I gave up. apparently he doesn't need them!
I can't understate how complex this software is - it's stock control, point of sale (including the usual things like birthday vouchers, discounts accounts etc etv), prescription dispensing, patient records etc. everything for a modern pharmacy. The australian health dept know about it and it's met all their criteria. it does everything.
It's mindbogglingly awfull bad code by any metric imaginable but yet it's robust, appears to be as-good-as bug free and has been able to be maintained (gov regulations for pharmacy change constantly so it's required major changes each year to keep up to date) and in production use for almost 20 years. oh, and it's fast :)
[Edit: looking at the other comments it seems I've replied to the wrong thing. I was actually writing a comment in response to this http://prog21.dadgum.com/87.html (Write Code Like You Just Learned How to Program) which was linked to from the main article]