Lime Text: Open Source Sublime Text clone
If there is one app I've always been thrilled to pay for, it's Sublime Text. I've purchased and renewed the licence ever since v1 came out. While it may not be open sourced, you can see it was created with a lot of love for code and openness. Today there are thousands of amazing plugins to enhance it. And though I fully respect the open source initiative, I, for once, am very happy to support / give some money to a peer developer who has made our world much better.