Sometimes, as part of the publishing workflow, you want to get feedback from people who don't need to access the backend of your website often enough that it makes sense for them to have their own user account. For these kinds of scenarios, where you need "one off" access to unpublished content, the Access Unpublished module is a terrific solution.
I had also looked at the Preview Link module, which is also good, but I like Access Unpublished better. Preview Link always generates a link with the globally configured expiry length, and makes it available as a tab on nodes for anyone with permission to access it. I like to keep my tabs row cleaner, so I like that Access Unpublished exposes it's widget within the edit interface. Also, as an editor, you can generate one or more links with a link-specific expiry.