1. "I find no arse-crack in it"
Dutch ("ik vind er geen reet aan"). This is boring, this does not interest me at all.
2. "All fart and no poo"
Singaporean English. Promises much but delivers nothing. All mouth and no trousers.
3. "To fart too high for one's arse"
French ("Péter plus haut que son cul"). To have ideas above one's station, to be too big for one's boots.
4. "Fur coat, no knickers"
Mainly northern English and Scottish. Looks good on the surface, but nothing underneath.
5. "All hat, no cattle"
6. "One who fucks in the dark"
German ("Dunkelbumser"). Someone who has sex with the lights off.
7. "He makes my shit itch"
British military. To describe someone particularly annoying. (Also: "He makes my fists itch", someone who brings out the violent urges in one.)
8. "Asparagus Tarzan"
German (Spargeltarzan). A thin, weedy person.
9. "As thick as a bull's walt"
Irish. A "walt" is an erect penis, so the described person is as thick as a bull's boner. Thick as two short planks, only better.
10. "May your house be live on CNN"
Serbian (A bog da ti kuca bila). Expressing a wish that you will be blown up by a bomb falling on your house.
11. "Tommy Two-Shits"
British. Someone who, whatever you've done, will tell you they've done better. As in, if you've had a shit, he or she will tell you they've had two.
12. "This came out of an arse"
Finnish ("tämä on perseestä"). That sucks, that sucks balls. As in "proge on perseestä", or "prog rock came out of an arse", i.e. prog rock sucks balls.
13. "Arse with ears"
German ("Arsch mit Ohren". An idiot.
14. "Couldn't pour piss out of a boot if the instructions were written on the heel"
American. Descriptive of someone particularly stupid.
15. "Wearer of a green hat"
Mandarin Chinese ("dài lǜmàozi", 戴绿帽子). A cuckold, a man whose wife is unfaithful to him. In the Tang dynasty, male workers in brothels apparently wore green hats. The suggestion is that the man's home is a brothel, and his wife a prostitute.
16. "Thick as manure but only half as useful"
17. "I shit on your mother"
Cuban and Spanish ("Me cago en tu madre"). Screw you, fuck you. Taking a shit on someone or something sacred is a common Hispanic interjection. For instance: "I shit on the communion host" (Me cago en la hostia), "I shit on God" ("Me cago en Dios"), "I shit on the Virgin" (Me cago en la Virgen), or, in a particularly offensive one from Cuba, "I shit in your mother's cunt" ("Me cago en el coño de tu madre").
18. "Rotten ballsack"
Dutch ("rotzak"). Dislikeable person, arsehole.
19. "Cow cunt"
Mandarin Chinese ("niúbī", 牛屄/牛逼). A positive exclamation, roughly comparable to "fucking awesome".
20. "Skipping cunt"
Dutch ("huppelkut"). A shallow woman.
21. "Take a shit in your hand, then slap yourself in the face"
Italian ("Caccati in mano e prenditi a schiaffi"). A cognate of "go fuck yourself".
22. "[He/she is] inside a fart cloud"
Argentinian ("en una nube de pedos"). In a world of his/her own, unconcerned by the world outside his or her foetid little cloud.
23. "Your mother swam out to meet the Japanese battleships"
Korean ("당신의 어머니는 일본어 전함을 충족하기 위해 밖으로 수영"). The implication being that the mother of the listener was a traitor, and a prostitute.
24. "Buddy fucker"
Dutch ("matennaaier"). One who has screwed over his friends – a Judas, a turncoat, a two-face.
25. "Fuck your ancestors to the 18th generation"
Mandarin Chinese ("cào nǐ zǔzōng shíbā dài", 肏你祖宗十八代). A particularly harsh "screw you" in an ancestor-worshipping society.
26. "You eat pubic hair with salt dip"
Vietnamese ("May an long dai cham mui"). It's not clear how well this translates, but presumably it implies bad things about the recipient's personal hygiene.
27. "The spring of cunts and the late winter of dicks"
Finnish ("Vittujen kevät ja kyrpien takatalvi"). An expression of shock or surprise: fucking hell, bloody hell, holy fucking shit.
28. "Fuck your mother's gods"
Romanian ("futu-ți dumnezeii mă-tii"). Pretty self-explanatory and part of a rich tradition of Romanian threats to fuck mother-related people and things. "Fuck your mother's dead relatives" ("morții mă-tii") is another.
29. "You are the result of a torn condom"
Hindi ("Phatele nirodh ke natije"). Self-explanatory. (It's worth checking out this extraordinary list of other Hindi profanities: I cannot vouch for their authenticity, but I sincerely hope that "chipkali ke chut ke pasine" really does mean "sweat of lizard's cunt", and that "chut ke pasine mein talay huye bhajiye" really does mean "snack fried in pussy sweat".)
30. "To have twisted testicles"
Italian ("avere i coglioni girati"). To be angry, to be in a bad mood.
31. "Lick my ass right well and clean"
German ("Leck mir den Arsch fein recht schön sauber"). Specifically, the title of a canon for three voices in B♭major, once thought to have been written by Wolfgang Amadeus Mozart but now credited to his contemporary Wenzel Trnka. The confusion is understandable since Mozart wrote a similar piece, Lech mich im Arsch, or "Lick Me in the Arse". Probably the classiest known uses of profanity.
With thanks to @dr_aust_phd, @maharafiatal, @jeffhow7, @tonyhill_7, @shmarxism, @maggyvaneijk