I am aware that certain apps, despite the best efforts, cannot be modded successfully [ such as Magzter ] or the latest versions of Tasker[ apparently, old versions do exist]. It might be ironical to ask this on a forum like this, but what apps have you folks found over the years that you found worth purchasing one off [ not subscription based, they suck, but as a one off thing]

Smart launcher. I use it all the time so I just bought it in support. Same with Poweramp.
Crayon icons; I just love so much.

Same with Poweramp.

I have heard lots of praise for this player. I think I should give it a go.

Edit: It really is a very good player. Worth a one time purchase. Good thing atleast the skins for the app are moddable here. Give a different look to it from the default one.

Same with Poweramp.
Crayon icons; I just love so much.

Poweramp is the best music player I've ever seen. Well worth $5 for a permanent, local license.