12. Ethnic humor
One of the more obvious candidates as a low form of humor is the mocking of certain ethnicities, usually limited to condescending, unfunny accents or punchlines about the Polish, but sometimes into the realm of outright xenophobia and racism. (There's a British comic whose material is actually largely about how much he hates the immigrants who work in various stores he frequents--if I could remember his name, I'd link him so you could be amazed that someone like that hasn't been ripped to shreds yet.) Anyway, this one comes in at the end, because in circles of largely intelligent people, it's pretty-well stamped out, or at least the worst forms of it are.
NOTE: Humor about race or racism isn't necessarily "ethnic humor," and if it's funny, it probably isn't. I wouldn't consider, say, anything in the British Office to be ethnic humor--it's not about people fulfilling stereotypes, it's about people having racist attitudes. Which is smart, not low.
11. "That character is so gay" humor
Kind of goes along with the above, but a lot more people are still willing to laugh at a line like, "Gay Bobby, you sure ate all those hot dogs fast!" even though it's no more intelligent than, "Black Bobby, you sure ate all that watermelon fast!" For that reason, it's higher on the list than ethnic humor. But just as low. Or lower.
10. Jokes comparing vaginas to roast beef
I theorize that anyone who has ever made one of these has either never seen a vagina or never seen roast beef. The latter seems unlikely, but I've heard women make these jokes, and I assume most of them have seen their own vaginas. In any case, whatever tiny bit of truth there was to it in the first place, it's been so completely washed under thousands of jokes with this at the core that it's really, really unfunny now.
9. Michael Jackson jokes
You'd think these don't exist anymore, wouldn't you? It's been so long since Michael Jackson been in any way in the spotlight that "Michael Jackson jokes" would seem to be kind of in the realm of "Monica Lewinsky jokes," where people are more likely to make fun of people making them than actually make them in earnest. So why was there one in the Christmas episode of 30 Rock, the smartest show on TV? (Kenneth: "Those are going to be the happiest poor kids since me and my brothers went to Neverland Ranch.") Oof. I have no fucking clue.
8. Jokes about how much spouses hate each other
Weirdly enough, I see this stuff show up nowadays in poorly-written college-kid stuff probably more often than I see it show up anywhere else. Which is doubly weird, because it's the demographic least likely to have any sort of real relationship with it. If your reference point for the relevence of a joke is The Honeymooners, you're probably a little out of touch.
7. Fake book titles with an author named Ima
Is this one too specific? If so, please pick up How to Write a Better List Entry Next Time by Ima Pologetic. Ima Nidiot. Ima Gonna Killa Myselfa.
6. Unnecessarily dated pop culture references
I'm looking at YOU, Family Guy! And Diablo Cody! These jokes are dumber than Raphael in that episode of Teenage Mutant Ninja Turtles when he got hit by the stupid ray! No? Don't remember it? That's because I just made it up! It would be no less terrible of a joke if I didn't!
5. Straight dudes doing something that looks kinda gay
I'm not talking about stuff like the Seinfeld episode "The Outing," where George and Jerry farcically have an argument that is perceived as a couple's argument, then wrestle with their own insecurities. I'm talking about stuff like the Seinfeld episode "The Doll," where Estelle Costanza walks in on her husband, Jerry, and the maestro playing pool without pants. (Okay, so Seinfeld was around long enough to do a lot of bad things as well as basically every good thing.) But seriously, what are we meant to think? That they're embarrassed because, obviously, gay people play pool without pants all the time? What the hell? I think a lot of this humor is based on a mode of thinking that goes something like, "Well CLEARLY it would be extremely insulting to be thought of as gay, so let's laugh at them." This crap idea also provided that atrocious "trying to get each other's hands untied" scene in Pineapple Express, an otherwise pretty good movie.
4. Jokes that vastly overestimate the power of drugs
"He smoked so much pot that he thought he was an airplane! We managed to stop him before he took off on a nonstop flight for Denver!" Pause for uproarious laughter from concerned parents, or someone else who believes that is in any way plausible.
3. "That's what she said."
You guys remember when The Office started doing this, but it was ironic, mocking Michael for being so stupid as to think that it was brilliant? And then people who were fans of The Office started saying it a lot, but unironically? Yeah, I don't get people.
2. "Come" puns
Similarly, I have no idea how anyone still laughs at something like, "Sorry you came late, but hey, at least you came, right?" Bonus negative points and a warrant out on your head if you pair one of these with the above.
1. Dead baby jokes
This is probably the ultimate in fake-edgy humor. Dead baby jokes are such an established humor trope that you are challenging absolutely nobody by telling one. Haha, you can laugh at gross things, congratulations, you are so cool. I will continue to laugh at funny things.