bfire writes "The term 'killer app' gets tossed around quite liberally these days. Nearly every piece of software released seems to be pitched as having the potential to send shockwaves throughout the IT world. In reality, there have been precious few applications which have truly changed the computing industry over the years. This article lists some of the top ten true killer apps that changed computing, from Phil Zimmermann's gold standard in encryption, PGP, to Dr Solomon's groundbreaking anti-virus toolkit, to Mitch Kapor who took the idea of VisiCalc for Apple and created Lotus 1-2-3 for DOS." Typical for top-10 lists, the choices seem pretty arbitrary — what changed your corner of the computing world?