Drafts, as I use it constantly. Also, I find Basecamp indispensable for managing teams of people and cannot believe it’s free for educators. Such a good quality application that saves me a lot of email and other noise.
I think the dev went through a rough patch, not sure.
Website has a blog post from May. They aren’t accepting money at the moment. Still works fine for me. It’s kind of my go to editor for a lot of things (multiple cursors, macros, and familiarity).
I check to see if I can register it every six months or so.
There are too many for me to think of anything like a complete list, but one that stands out is Blink Shell for iPad. It makes working on remote servers from my iPad an absolute joy. I’d happily pay for it again.
I pay for services like Apple Music, TripIt Pro, and Mobile Passport. And I regularly pay for upgrades to apps like BBEdit, Hazel, Downie, and Permute. But I have no need for any subscription apps so far. For example, the free version of Drafts and Instapaper are all I need.
But I like to thank developers for their work. Since the days of shareware I’ve been occasionally “tipping” developers, sometimes though a “Tip Jar” included in an app like Pedometer ++. And sometimes by subscribing to an app for 2 or 3 months a year.
And if I ever find myself needing the premium features of say, Drafts or Instapaper I’ll subscribe full time.