Ask HN: What app do you use to collect ideas?

Hey everyone, I'm working a major refresh for an idea management app I'm working on. I would really like some feedback from the community on what apps you use to collect ideas and why? Is it the speed or simplicity of the interface? sharing? search? Something else? Totally fair if the answer is 'notes'. If it is, why do you think that is? I put stuff in my notes all the time - but can never find it if its older than a week usually.

Looking forward to your thoughts!