What was the worst bug you've ever solved ?
bkz: After having launched our product I was spending some time reviewing commits together with the senior tech lead. Still to this day I can recall the commit number, the filename and write down the code from memory responsible for what turned out to be the source of a bug completely wiping out our users computers. Someone had mixed uncommenting a piece of code together with fixing a bug which hid the fact that some horrible code was active in the product. It took us 5 minutes to produce a fix and push it out to the update servers. Did we end up wiping someones computer? Yup, about a dozen known cases including a couple one in-house. I don't even want to think about how many actual cases there were, considering that we had about 2 million downloads of our product before the bug was fixed.