Voice modifier software?

That just sounds like echo on someone doing a death metal voice. It doesn't really sound too pitch shifted if it is at all. Most music applications will do that.

Depending on how deep you can make your voice you can just do a death metal voice and add a little echo or reverb to it. If your voice isn't low enough pitch shift it down an octave or two, then add reverb or echo.

You can get it with almost any music applications, there are so many out there. I use Goldwav to capture some sounds, you can get a demo and use it for 30 days, has all the stuff you need. You can get it in simple apps too for your phone now. Basically look for audio software that has pitch shift, echo, and reverb, and you can make it happen. Here are some software options.

Goldwav

Nuendo

FL Studio

Ableton

Garage Band

Absynth

etc...Like I said, most any audio editing program can do it nowadays.

It's done with video editing software like Sony Vegas, or Camtasia. I suggest Sony Vegas because it has many more audio editing modules.