Purely on the basis of visual appeal, I think I'd go Gunslinger+Operative. Sniper has little variance in attack animations. it's just aim rifle=>fire, aim=>fire, send attack drone, fire, while Gunslinger has all fun "gun kata" dual blaster stances, the finisher looks a bit more fun (two massive energy bolts with thick smoke trails are plain BA), etc, etc.
Operative, on the other hand, seems to have gotten a lot more love, animations-wise. Healing animations are a lot more detailed. Whereas Scoundrel just stands there, pointing a remote at people, Operative shoots darts, uses hypos on himself, has a more interesting diag scan animation. As far as damage is concerned, Scrapper looks kind of clumsy. Sure, damage is calculated at the same time, but the whole shotgun business just looks slow. Punching a lightsaber-wielding Sith in the face, while fun, is kind of silly, to be honest. Unless it's done by a TKM... and Smuggler is anything but a TKM
I like Operative's knife animations better because they are more fluid and quite varied, despite the very basic concept of stabbing someone with a sharp vibroblade.