Even the instruction manual for the Rezound didn't list this gem. Want to block a specific caller? If they already called, go to call history, long press on the number, and a menu pops up with an option to block caller. In the call history mode, pressing the menu gives the option to see a list of blocked callers, and another menu press allows you to add a number either manually or from a list of contacts.
Who needs an app or to pay VZW for their unlimited blocking feature?
Controlling who can call me is important to me, and I'm glad I stumbled across this feature.
Works on my wife's HTC Incredible 4G also.
EDIT: The "blocked caller" goes to voicemail and can leave a message. (I tested this out). If they do, the voicemail is indicated on the phone. I like this feature, so if I inadvertently block an important caller, they still can contact me. Removing blocked callers is an easy step through the call history menus.