It's easy to take lots of photos with your iPhone. But when you're ready to wipe the slate clean—without wiping out other photos you've synced to your device—there's no obvious way to completely (or even selectively) use your Mac to delete the photographs you've taken with the phone.
A couple of years ago, blogger Colin Devroe came up with a clever way to make that happen. His solution relies on OS X's oft-neglected Image Capture utility. (I like to use Image Capture to prevent iPhoto from launching every time you sync your iPhone.) To implement it, connect your iPhone to your Mac and launch Image Capture. That app will see your iPhone as just another camera.
In Colin's original hint, you'd then download all the photos and tell Image Capture to delete them all when it's finished. Turns out Image Capture now offers an easier, faster way to do that: You can selectively delete photos without ever importing them from your phone. (I've been unable to ascertain exactly when this became possible.) In Image Capture, Command-click all the photos you want to delete. If you really want to delete everything, just hit Command-A or choose Edit -> Select All. Then, at the bottom of the Image Capture window, click the delete icon—it's the red No symbol. Image Capture will ask you to confirm that you want to delete all those photos. And if you tell the app that indeed you are ready to bid all those pictures adieu, it will delete them immediately.