Assassin is quite good, lots of tools in the box, you can sacrifice your companion for health (kind of lame tactic, that one), stun, CC, knockback, incapacitate, useful defensive cooldown - you even have a tanking stance, sprint, Force Shroud (think Cloak of Shadows) and Force Cloak (Vanish). Good burst aswell (procced Maul is devastating) + good execution ability (Assassinate, low cost low cd). Less stealth focused play than the Operative though.