As others have indicated, it seems like there are more put-downs relating to sexuality and gender roles, physical appearance, and ethnicity than there are with any connection to physical or mental disability.
Waste of space
Douche or douchebag?
How about
“You complete tosser”
Yeah, I came in here to say “douchnozzle” and the slightly dada-esque “douchecanoe.”
That’ll just get you a :dubious: and/or 
around there parts. It sounds like a basketball term or something.
Oooh! Oooh! I just thought of one: straight guys calling another straight guy a “pussy.”
Monkeyfart
Shitweasel
Hamster Smuggler
Scrote
Rabbit Catcher
- Actually, Rabbit Catcher is a joke insult in my family. Also, I have a distant relative who posts on this board, and I’m pretty sure an incidental part of his job is sussing out hamster smugglers - among other exotic animal smugglers.
Yahoos, turkeys, tools
You stink
You suck at that
I think you can lump insults into some general categories:
Unfavorable comparisons with animals (jackass, bitch)
Genitally based insults (cunt, dick, pussy, scrote, cock)
Sexual practices or habits (cocksucker, motherfucker, carpet muncher, fag)
Association with bodily fluids (asswipe, douchebag, asshole)
Humorous neologisms and mashups of other insults (asshat, douchecanoe)
Insults to intelligence that make reference to being so stupid you’re disabled (mouthbreather, idiot, moron, “special”, slow, tard/retard)
Other insults that refer to a disability – this strikes me as the smallest category; actually “lame” is the only one I can think of.
Ummm. . .I was gonna say douchenozzle. Scumbag.:mad:
Nitwit, numbskull, numbnuts, airhead, meathead, nimrod, pond scum, the stuff pond scum scrapes off the bottoms of its shoes*, four-eyes, tinsel teeth, hillbilly, hick, trailer trash, rube, son of a bitch, etc., etc. Now I have to go look at pictures of kittens to rebalance my brain.
- per Carla on Cheers
Bessie Braddock: “Sir, you are drunk.”
Churchill: “Madam, you are ugly. In the morning, I shall be sober.”
Actually, idiot comes from Greek and it originally referred to someone who, having the right to vote, did not use it and eventually got stripped of it. Not about IQ at all. The use that’s about IQ is the distorted one.
Yo’ mama
You need to establish some ground rules - as already discussed upthread, “idiot”, “retard”, and “cretin” are probably unacceptable because they refer (at least historically) to defined mental disability, but we don’t know whether you’ll accept “stupid” or not. To take it one step further, how do you feel about “one knife short of a drawer”, “the lights are on but nobody’s home”, and other humorous ways of saying someone falls short in the brains department? Do those terms refer to disabilities, or not?
Likewise, what about derogatory terms that informally refer to mental illness? Nut job, whacko, crackpot, crazy, or (really borderline here) ditz? Or what about terms that refer to someone’s physical appearance - pizzaface, fatso…?
I’m pretty sure that some terms referring to how people tend to behave would pass whatever tests you choose to set: dirtbag, scumball (or scumbag or dirtball) and the above variants on douche.
“You horrid little man”
You’re the lowest form of life on Earth. You are not even human-fucking-beings! You are nothing but unorganized grabasstic pieces of amphibian shit! Because I am hard, you will not like me. But the more you hate me, the more you will learn: I am hard, but I am fair! There is no racial bigotry here! I do not look down on niggers, kikes, wops, or greasers; here you are all equally worthless! And my orders are to weed out all non-hackers who do not pack the gear to serve in my beloved Corps! Do you maggots understand that?
Wanker?
Lout! Clod!
Then you should have mentioned that in your OP.
Nava - you got a cite for that? I was told that in my US Government And Civic Responsibilities class senior year of HS (aka the Rah Rah USA class) and it seemed suspect to me, so I looked it up…from what I could tell, it referred to people of deficient intelligence who were therefore not permitted to vote. On the other hand, that was before the internet…