1) Changing something in the README
2) Changing a typo
3) Changing the CSS color of something
Those are the very basic cases all orgs could benefit from doing in a no-review way. If you want to treat your developers like adults, and have some faith in the test suite they've written, you could also allow no-review for cases such as: 1) Developer fixes an obvious bug in an obvious way, writes unit tests to ensure that there are no regressions.