The Imperial Agent is a very exciting character in Star Wars: The Old Republic, but recently a veritable ton of information released on the Sith Inquisitor. Wielding the Force as the power behind the throne, the Sith Inquisitor discovers that true power rarely makes overt displays of violence. Subtlety, deception, and patience are viable paths to glory for this assassin in the shadows.
Sith Inquisitors can fufill the roles of tank, healer, and damage-dealer. They can be both melee and ranged, hurling lightning bolts and lightsaber strikes with impunity. Obviously, this class appeals to me in several ways; 1) they throw lightning, 2) they are a jack of all trades, 3) they like to use double-bladed lightsabers. They're basically space-shaman with laser swords; utility classes with nasty damage capabilities and freakin' lightning bolts.
Have I mentioned that Inquisitors can throw lightning?
Sith Inquisitors have two advanced classes; Assassin and Sorcerer. Assassin seems to operate more along the lines of a melee stealth class and the Sorcerer leans toward ranged energy attacks. Both classes can stealth and both classes can dual wield (at this time).
Inquisitors are designed to be a support class, but they have the option of being Assassin tanks. How this will work is unclear at the moment, but I expect a great amount of detail (as well as a beta announcement) at E3 this year.
All in all, the Inquisitor will be the second class I roll in The Old Republic; it was formerly my favorite, but the allure of the Agent is just too strong.