My "app" of choice is a pad of paper. Writing things by hand helps you remember better (not my opinion, proven in studies). Crossing things off a piece of paper feels better than deleting, because you see the list getting completed, and see how much is left. The "app" is always open on my desktop.

I've tried many electronic apps. Actual paper works the best, until something like "remarkable" gets so cheap I can replace my pad.