On the code side, I love what I'm doing right now with Neo4J and the DoerHub badges and topics. I am trying to use graph database searches to surface people who are strong in areas you are weak in and weak in areas you are strong in when you do a search for a topic. Also trying to apply NLP to ensure the system recognizes related topics (cancer and healthcare for example). My latest work is usually my favorite.
On the non-code product side I hypnotized NBA.com users with the Social Spotlight product you can see on its homepage now. It used to generate higher duration of stay than any page on the site including video. I did it by re-created the "Monument to Change" Stanford GSB flipping tiles effect with an unending river of the most interesting images and tweets from the NBA conversation on social media. There was some FOMO mixed with good content, mixed with a mesmerizing effect.
On the brick and mortar side I created a forge-detecting technique for printing coupons for a bakery in Bulgaria by mixing Inks with different reactions to water. Had to do it because competitors were trying to forge the coupons and put the bakery out of business. In the end though, the hack ended up getting an employee of 10 years arrested, because, as it turned out, he was swapping cash for his own home-printed version of the coupons.