I've played a Barbarian (to 5th level), Cleric (to 4th level), Rogue (to 6th level), Fighter (only at 1st level), Ranger (to 2nd level), Paladin (to 5th level), Sorcerer (to 3rd level), Oracle (to 12th level), and Bard (in progress) so far.
I've also played a Commoner to 7th level (so far). It was amusing, and she's technically not dead yet. We go back to our 4-commoner party every once in a while and have a blast struggling against things that other classes could crush without a thought.
The only class I've never even seen played at our table is the inquisitor.
As for which class is my favourite, I hold soft spots for the barbarian since it was my first class, and oracle since I spent so much time with it, but I think my favourite is my current class, the bard.
I think it's about being a jack of all trades, but the bard is also just plain fun to play.
Even when my bard was suffering strength penalties throughout the entire storming of a fortress, I didn't really feel affected like I'm sure my old barbarian or fighter would have. I was still able to help everyone just as well as always with bardic performance, I was able to cast my spells just as well, I was able to do things like flank for our sneak attackers, and I was still able to use my skills to great effect. I think a class that focuses more on one specialty couldn't manage something like that.
My favorite class, in theory since I haven't gotten to play it yet, is the Vivvesectionist Alchemist. And yes, I feel the need to specify archetype because I find almost every aspect of the Bombs mechanics to be dumb. V.A. seems like it performs like a Rogue that doesn't suck, and the assortment of freak show self-experimented body horrors you can get via discoveries are cool.
My current party has a 3-armed (soon the be 4-armed), dual-wielding vivisectionist. The character is extremely cool to watch, looks fun to play, and has bumped the alchemist class up to be the next one I intend to play.