Ask HN: What's your ideal tool for collecting ideas or brainstorming?

Does the current tool exist? Is it Trello? Why? I'm working on a startup that's trying to solve innovation management and we want to develop the best experience for capturing ideas possible. I would love to know what the HN community uses for ideas and not 'issues'. What I mean by that is you are probably putting things you are actioning on for sure in something like JIRA or Github right now (I'm a dev, so that's where my head is at). Thanks in advance for sharing!