At BlizzCon 2013, I was lucky enough to sit down at one of Blizzard's demo machines and play through the first part of the new Diablo 3 Reaper of Souls expansion as the new class, the Crusader. This article will have some spoilers for the new content, so if you're trying to avoid that, beware.
The demo character was a male Crusader, set at level 33. He came with a few powers preset, which I used for the demo. For the left mouse button, a single target Slash attack struck the enemy with holy power. For the right button, Fist of the Heavens sent a huge beam of Holy Energy from the heavens around the Crusader, followed up by electric bolts that split off and attacked any enemies still standing. This right click, of course, cost Wrath, which is the Crusader's resource and regenerates like a combination of a rogue's energy and a death knight's runic power from WoW.