Mistakes to learn from

There's some quote to the effect that experience means that you've made mistakes, and have learned from them.  I started doing ASIC design in 1983, and not only have I learned from my mistakes, I'd like to think that I've learned from other peoples mistakes that I've observed.

This page is a collection of mistake stories. I would be glad to add stories from other people as well.  The whole point being that maybe someone else can also learn, and also maybe be a little amused.

I'll try to give fairly good titles to the mistakes...

Always be careful with clock
Power (VDD/VSS) is actually important
Test the Tester