I know that this is a rather odd question as you can't really tell which class is the most fun to play for me but right now I just can't decide which class I want to play. Played a Jedi Shadow to level 44 before New Years Eve and hadn't much time to play him since then. When I played him again a week ago I came to find that I was absolutely bored by the story and my companions as well as Republic in general. Now I switched server (for a new legacy, you know) and started every Imperial class. Got a level 20 Operative, level 13 Powertech and a level 12 Juggernaut (and some low level Sorc). The problem for me now is that I enjoy every class.
I definitely play the classes either as a tank or a healer. Played restoration Shaman for most of my time in World of Warcraft and while I know that I won't get a class that's near the Shaman's gameplay, the healer who has the most in common with him would get my attention. I wanted to play tank for a change (been a healer in MMORPGs for years now) but I'm completely lost. Just gimme some input mates!