Ask HN: What code review tool do you use?

We're a small team looking for a good code review tool that allows us to move fast and break stuff.

Most of the tools out there seem to be focused on pull requests. Our team does do pull request reviews through Github, but we frequently will merge PRs that aren't "ready" for the sake of getting features out.

We've looked at Codiferrous (seems kind of unsupported) and Gerrit (but we don't want to host it ourselves) and a few others, but we're a bit at a loss.