I don't have one big thing, but several small things that I am proud of having done. I wrote an application to assist in comprehensive cardio and vascular screenings that has been used to [hopefully] save many lives. I wrote an application to process prescription orders using HL7 for a national hospital system to print out shipping labels for their prescriptions. I designed a never implemented system to allow patients to securely control, share and revoke, their medical information between pharmacies, doctors, and other health care providers (if such a system were ever implemented it would have a tremendously positive effect for a lot of people). I wrote a Memcached port for Windows. A couple of libraries to assist other developers. My proudest accomplishment though has probably been mentoring new software developers.