I went with Don Rickles. I’ve seen clips of him on talk shows. He’s not funny at all, just rips out insults, often ethnically based, and then alternates that with cloying false humility. It was quite repulsive. Maybe there is some trove of him being funny somewhere, but I can’t imagine it.
I have to point this out because no one else is going to take the time:
Joe Rogan is an annoying blowhard who thinks making fun of people he doesn’t like is pure Comedy Gold. Here is a bulletin - try adding just a little bit of wit.
Thanks to the OP for adding his name to the list.
No, you’re not. The only poster child for “reconsider plastic surgery” who can top Ms. Rivers is Jocelyne Wildenstein aka Catwoman.
I agree with this statement.
I tried patiently to capture the poll stats at the 100 mark, but they jumped from 98 to 102 in a flash, so all I have to compare with the sort in Post #25 is:
View Poll Results: Who is the most annoying/unfunny stand-up comic? Multiple choice.
Carrot Top 47 47.96%
Larry the Cable Guy 35 35.71%
Gallagher 34 34.69%
Andrew Dice Clay 33 33.67%
Carlos Mencia 29 29.59%
Dane Cook 27 27.55%
Gilbert Gottfried 26 26.53%
Lisa Lampanelli 20 20.41%
Roseanne Barr 17 17.35%
Richard Lewis 17 17.35%
Joan Rivers 16 16.33%
Artie Lange 15 15.31%
George Lopez 14 14.29%
Bobcat Goldthwait 13 13.27%
Sam Kinison 13 13.27%
Louie Anderson 12 12.24%
Daniel Tosh 12 12.24%
Whoopi Goldberg 11 11.22%
Bob Saget 11 11.22%
Andy Kaufman 10 10.20%
Don Rickles 10 10.20%
Sarah Silverman 9 9.18%
Howie Mandel 8 8.16%
Dennis Miller 8 8.16%
Ray Romano 8 8.16%
Adam Sandler 8 8.16%
Robin Williams 8 8.16%
Gabriel Iglesias 7 7.14%
Richard Belzer 6 6.12%
David Brenner 6 6.12%
Joe Rogan 6 6.12%
Jerry Seinfeld 6 6.12%
Milton Berle 4 4.08%
Rodney Dangerfield 4 4.08%
Phyllis Diller 4 4.08%
Jeff Foxworthy 4 4.08%
Paul Reiser 4 4.08%
Henny Youngman 4 4.08%
And of course there’s also… 4 4.08%
Jonathan Winters 3 3.06%
Maria Bamford 2 2.04%
Bill Cosby 2 2.04%
Steven Wright 1 1.02%
Lenny Shultz 0 0%
Multiple Choice Poll. Voters: 98.
As I stated above, I still consider that bottom (<5%) group as a tacit endorsement of their funnyness.
Who is Lenny Shultz?
Wow, and he was so good in those AT&T commercials, too!
I voted for Maria Bamford, Milton Berle, Carrot Top, Dane Cook, Andrew “Dice” Clay, Jeff Foxworthy, Whoopi Goldberg, Gilbert Gottfried, Gabriel Iglesias, Larry the Cable Guy, Howie Mandel, Carlos Mencia, Joe Rogan, Ray Romano, and Lenny Schultz. I would also add Jeff Dunham, Greg Fitzsimmons, and Bill Engvall to this list.
You are joking, are you not?
But Ron White is actually quite funny.
As is Bill Engvall, but so what? 
Or of their relative unknownness, i.e. Lenny Shultz.
You know what, so do I. And I’m the OP. 
I also regret overlooking Margaret Cho.
mmm
Paraphrased from an older Letterman monologue:
mmm
After the Izzard/Gervais poll, which motivated me to check out some of Izzard’s stand-up, I must say that he belongs at the top of my list of unfunny. Not particularly annoying, mind you, just not funny.
Mustard, is there a reason that both of these didn’t make your poll?
Gallagher deserves extra unfunny points for the whole situation with his brother. Not that he was such a huge dick for suing his own brother for impersonating his act, but for having such a shitty, weak, cliched act that it could be successfully impersonated by his brother.
For some reason, he is playing Knucklehead’s Saloon in Kansas City in July. This is a music club, and has never had a comedian before. I suspect that record will remain unbroken.
Thirding the vote for how funny Bobcat is.
His bit about insulting the surviving members of Lynyrd Skynyrd is funny.
And he has a good touring with Nirvana bit.
Whenever I’ve heard him on the radio he has been awesome.
Joan Rivers when she was young was a first rate standup. Her face and act have both morphed into something scary now. But she was on top for a few years and deserved it.
I omitted Larry the Cable unfunny Guy. My mistake.
Good point.
I didn’t / don’t know who Izzard is. As for Gervais, I was not under the impression that he was regarded as particularly annoying and/or unfunny. I think he can be very funny.
mmm
Another sorted summary from just now:
View Poll Results: Who is the most annoying/unfunny stand-up comic? Multiple choice.
Carrot Top 58 47.93%
Larry the Cable Guy 42 34.71%
Gallagher 41 33.88%
Andrew Dice Clay 40 33.06%
Dane Cook 39 32.23%
Carlos Mencia 37 30.58%
Gilbert Gottfried 29 23.97%
Lisa Lampanelli 27 22.31%
Joan Rivers 22 18.18%
Roseanne Barr 20 16.53%
Richard Lewis 19 15.70%
George Lopez 19 15.70%
Artie Lange 16 13.22%
Daniel Tosh 16 13.22%
Sam Kinison 15 12.40%
Sarah Silverman 15 12.40%
Andy Kaufman 14 11.57%
Whoopi Goldberg 13 10.74%
Bobcat Goldthwait 13 10.74%
Bob Saget 13 10.74%
Louie Anderson 12 9.92%
Howie Mandel 11 9.09%
Don Rickles 11 9.09%
Gabriel Iglesias 10 8.26%
Ray Romano 10 8.26%
Jeff Foxworthy 9 7.44%
Dennis Miller 9 7.44%
Joe Rogan 9 7.44%
Adam Sandler 9 7.44%
David Brenner 8 6.61%
Robin Williams 8 6.61%
And of course there’s also 7 5.79%
Richard Belzer 6 4.96%
Rodney Dangerfield 6 4.96%
Jerry Seinfeld 6 4.96%
Milton Berle 5 4.13%
Phyllis Diller 4 3.31%
Paul Reiser 4 3.31%
Henny Youngman 4 3.31%
Maria Bamford 3 2.48%
Jonathan Winters 3 2.48%
Bill Cosby 2 1.65%
Lenny Shultz 1 0.83%
Steven Wright 1 0.83%
Multiple Choice Poll. Voters: 121.