Although I'm sure this subject has been discussed to death (I didn't scroll very far through all the threads), I'd like to talk about our favorite professions because I enjoy gushing over mine and reading about why others love theirs.
Necro and Engi are my favorites.
As a WvW main, I just love having the ability to completely turn the favor of a fight when playing Necro. My long time main and most played class, it's one I seemingly never get tired of. For the 7 years I've played it there has only been one time that I was unable to enjoy myself, and that was for a few months shortly after POF release. Otherwise, I have a nearly daily moment of "god, I love this class so much." There isn't a single fight I find myself in where I wish I was on something else. The ability to strip/corrupt Boons and having such a tremendous amount of area pressure is so satisfying and fun to me. I have never been bothered by the fact that Necro struggles to handle focus fire or that it is generally immobile because I feel the strengths it possesses more than make up for it's weaknesses, and I enjoy how rewarding it can be to know how to position yourself and pick your targets. Unlike most things I've played I feel I can see the results of my actions a lot more clearly with Necro and it gives such a great sense of accomplishment.
With Engi I just enjoy the "in the moment" options that the class provides, something others don't seem to have. Depending on the build of course, it feels like I have a gadget to solve every problem. I love the versatility of Engi that allows me to play the same class in completely different ways, and I love that even skills that aren't the greatest are super fun to use. Engi feels like a toy box of excitement where everything has a bit of a surprise to offer under the right circumstances.
My Youtube: Coconut Racecar
Necromancer | Maguuma | Diamond Legend
[YWY] Weeping Valley | [PANG] Save The Cave