I'm going with Imperial Agent/Operative as most fun class. I have 8 characters, half on Empire and half on Republic each in teens to and 20s, so no sense yet on endgame. However, so far I'd say the Imperial Agent has one of the most fun stories (tho I think the Inquisitor is best so far and best opening is the Smuggler). More imporantly, the playstyle is the most varied and hence most fun to play, don't get bored. Its kind of visceral and savage and I can attack via stealth with my vicious knife (like I'm supposed to) or if I like can play more like a sniper or mix it up. Also, when I'm feeling lazy I might just heal Kaliyo and let her do the work. She is also the craziest companion I've encountered yet--another plus!