Yeah, this one got me too.  I just assumed it was a regular Micro USB port.  Then, I got home and noticed a different kind of plug.  I was pissed, thinking I had to buy a new car charger.  I even gave my old one to the wife.  A few days later I went into a different Verizon store.  I asked the salesman if he had car chargers for the HTC.  He said sure, and showed me one with a regular Micro USB plug.  When I explained that the Rezound had a different kind of plug he looked totally perplexed.  How do some of these people get hired and keep a job if they know nothing about the products they sell?  I had to have him open a cord package from a new Rezound and point out the difference.  When I saw the display model with a standard Micro USB plug inserted, I realized they are interchangeable.  Doing some research online I discovered HTC's version is called ExtMicro USB.  It's supposed to be a much more secure connection.  I concur.  When I plug it into the phone it feels solid as a rock, much more so than the standard plug.  I had no intention of buying a ridiculously overpriced car charger ($30.00) from the Verizon store.  I just wanted to see what kind of charger they were selling.  I ended up buying a brand new one for $2.99 (with free shipping) off of eBay.
RH