curl -I and wget -S are particularly helpful when debugging redirects.

Sometimes I migrate URL schemes, and set up permanent redirects in my .htaccess files. Testing them in a browser is a real pain, because browsers cache the redirect (which is the point of having a permanent redirect), so even if you change the .htaccess, you still get the old response. And pressing the refresh button is no help, because that reloads the destination page, not the source of the redirect.

That's when a non-caching command line client saves your day.