My guess, over the long run, is that it'll be Cryptopals. Which is funny, because it's just a blog post that we chopped up into email challenges because I didn't want to give [redacted] a bunch of new terminology to use against me in stupid Twitter slapfights. Dumb reason, good outcome.
Although not an app, I think the most impactful thing you've built is your reputation on Hacker News. You helped a lot of people. What's left of the discussions will help many more over time. I learned from you, too.
I've been off HN a while with a new life (see profile). In case I didn't, I wanted to make sure I apologized to you for being such a troll on here. You and anyone else. I hope you're all doing well. I've prayed God blesses all of you, your families, and grants you the forgiveness and eternal life of Jesus Christ. :)
https://cryptopals.com/