I’ve been a user of the GTD method for many, many years, so any app I use needs to be GTD-specific.

Currently, I’m using Nirvana - have been for about 6 years. I like it so much, I paid for the lifetime sub, so haven’t really bothered to look elsewhere since.

Highly recommend pairing this with David Allen’s GTD and Rainer König’s excellent course Getting yourself organized with Org-mode