For me, it’s journalists. They’re so fond of themselves, they pontificate on world issues, they rush to trouble spots and make them worse, they praise and honour one another incessantly, they suppress stories that need to be told, they take themselves do seriously. Well, not all, of course.
Is it only me who wants to punch Mike Wallace or Tim Sebastian’s lights out when they strut their stuff?
Other nominations, please.
Spammers and telemarketers.
Professional torturers, Police Interrogators & Prosecutors.
Politicians.
Parking Inspectors.
I think there’s more dignity in being on the dole than accepting your lot in life as a parking inspector.
I hate professional activists (even if they are eager college students that don’t get paid) of any sort regarless of what their position is. If I agree with their position, I already have it my own. If I don’t, then they are never going to convince me otherwise. I am stuborn that way.
‘Professional’ students.
Those insufferable nontraditional college students who just come back to audit classes or finish a degree 3 credits at a time and who take up class time babbling endlessly about how they learned X, Y and Z in the real world and that invalidates the theory we’re talking about.
Of course, this doesn’t apply to all, or even a majority of, nontrads. Just a special, tact-challenged subset.
Human resource professionals
I second that. The ones in my English department are the worst. They want to be teachers, but they never do the assignments on time, they never get to class on time, they never actually stay on topic, and they bitch about the profs more than any traditional student I’ve ever heard. They make me crazy…especially because like you said, the majority of nontrads are great students and great classmates.
Supermodels. Ostensibly, they’re displaying designers’ fashions, but hardly any real women are shaped that way, so it’s not about the clothes at all anymore…
Anyone who has no learned/cultivated skill and does a job that a lesser primate could literally be trained to do, yet is unionized and has the audacity to STRIKE.
That includes, but is not limited to, the union of the people who do nothing more than sit in the booth and operate the gate in parking garages who recently actually went on strike because full benefits and $20/hr WASN’T ENOUGH. They’re already making more than me, with my master’s degree!
NUNS!
ooooohhh. . . they walk around in those sexy outfits strutting that fine booty, but can I touch, can I, please?
nooooo, you may not.
I just wanna punch 'em.
I’ll nominate insurance adjusters.
When my new car was totaled (other guy pulled out in front of me), the adjuster (from my own insurance company! We had the same one) made me argue for every nickel and dime on the value. “I think that a sunroof reduces the value of a car.” Well, Mr. Smart-ass, you didn’t write this here blue book, and it says I’m entitled to fifty bucks for it. He was so rude to me when I was already upset, he had me in tears. I had to sic Mr. S on him.
Then my sister married one. He’s a jerk for many other reasons, but she told me once that he thought it was “cool” to go out and look at the wreckage of people’s lives and dreams. Asshole.
(Granted, that’s a sample size of two, but so far the jerk rating is running 100%.)
Marketing people. I’ve worked with a lot, and not one of them has been anything less than an arselicking snake in the grass fool who knew little or next to nothing about what it was they were supposed to be marketing.
If had to pick just one, it would be the self-righteous, left leaning element of the press. I despise snobbishness when it not me being the snob. 
If I can get away with listing all that I dislike, then I’ll list:
Politicians
Trial Lawyers
Political/Social Activists (both ends of the spectrum)
Telemarketers
Abrasive salespeople
The self-righteous elements of the clergy
Anyone in any profession that has an ego bigger than my own. 
Salescritters.
I have to deal with a lot of vendor representatives. Most of them drive me nuts (granted, it’s a short drive). They call at the worst times, offering products of dubious value in our enviornment, insist that they are exactly what we need, and won’t take “NO” for an answer.
All that said, a GOOD salescritter can be incredibly helpful. When I have a need, and a salesman can look at the situation, understand my requirements, make serious suggestions as to the best tool for the job, or even suggest how to modify the job to make it work more effectively with or without his products, then a salescritter can be a great asset.
Unfortunately, the ratio is about 99% to 1%.
Realtors.
I’m sure there are lots of nice, pleasant, competent realtors out there - I just haven’t met any of them.
I’d tell you about the various ones we met when selling the house, but that’s a subject more fit for the Pit.
I find it odd that nobody’s mentioned mechanics. The last time I saw a list of most hated professions they were up there with lawyers and politicians. Or maybe that was a least trusted list of professions.
Marc
Middle managers everywhere.
I may have met at least one that wouldn’t hesitate to screw you to cover his or her own behind, lie and withhold information to their own benefit, and generally be petty little fu… er… turds. But I can’t think of any.
I hate and I mean positively loathe short-sleeve women’s suits. They’re just so fucking wrong. I always say they look like something an HR person would wear.
Quite often, I’m right, too.