Like Dutch, Afrikaans has two words for some body parts: a human word, and an animal word which is also used on people as an impoliteness.
Mond is the word for person's mouth, and bek is the word you use when refering to an animal's mouth. Hou jou bek! is equivalent to "shut your trap!". "poote" refers to the hooves or paws of an animal, and "Kry jou poote af!" is much like "keep your paws/mits off!". A word of warning though, in Dutch "hoofd" is the polite word for head, and "kop" is the impolite one. However in Afrikaans "kop" is the only word for head and is not impolite.
Voetsak or Voetsek meaning "go away", literally "foot-drop", is what is usually yelled at a dog that you want to chase away.
To neuk someone is to hit them or otherwise interfere with them. "Ek sal jou neuk!" could be translated "I'll get you!". Literally it means "fuck" but it's never used that way.
Yissus or yussus is an exclamation very much like Jeez, being an exclamation derived from Jesus. Likewise, Yirre or yerre derives from "Herre", i.e. "Lord".
A bit biting
A common threat is to moer someone, to fuck them up, which may come from "moord", i.e. murder, "I'll kill you"; and Jou moer, which I have no idea how to translate.
In less crass circles, bliksem, meaning lightning is ued to express suprise, and donner thunder meaning a severe beating, is often used, for e.g. ek sal jou bliksemse moer donner which could be translated roughly as "I will beat you black and blue", but is actually better left as is.
A relatively mild term is doos literally a box or container, about equal in nastyness to calling someone a twat or prick, but has more connotation of stupidity and/or incompetence. This is a very common word to refer to anyone who has just done something stupid or objectionable.
kak is shit or crap (both the noun and the verb), as in jy praat kak: you are talking crap, Hy's vol kak: he's full of shit or gaan kak in die mielies: go shit in the fields or the variation Gaan kak in die bos Go shit in the bushes.
Kak is also used as a general-purpose negative word in both English and Afrikaans speech. E.g.: Q: So, how was the Movie? A: Kak!.
Fuck, the all-purpose English swearword, is translated as fok, and is heared as an adjective along with blerrie (bloody), as in e.g. Daai blerrie fokken ding That bloody fucking thing.
I need also to mention the word "visblik", a fish-can, i.e. a tin can used to contain fish, such a sardine can. It's sometimes a standin for harder words, and was the subject of some hilarity when we were children, but it's still an allusion to a slimey box that smells of fish.
piel refers to the external male gentalia.
Attention: If you are a noder of a sensitive disposition, read no further, for the following material could be found offensive. I didn't invent any of these, don't blame me for that.
Afrikaans insults, or at least the variety that we come into contact here in Cape Town, tend to be crass and obscene.
The cursee's mother is a perenial topic, as in the single most popular Afrikaans curse: Jou Ma: Your mother.
Often Jou ma is elaborated upon, and in fact it is often just a shorthand for Jou ma se poes: Your mother's cunt
Other elaborations are Jou ma se ma: your mother's mother, or Jou ma se ma se poes, Jou ma se stink poes:You mother's stinking cunt, Jou ma se hond se poes Your mother's dog's cunt, jou ma se ma se hond se poes, etc. and many elaborations upon these.
Jou ma se naai Your mother's fuck is another variation. The word naai refers to the action of a sewing machine, and is the most common equivalent for the literal verb uses of "fuck".
Other elaborations include:
Jou ma naai vir viskoppe daar by die docks: Your mother fucks for fishheads down at the docks.
Jy was uit jou ma se gat gebore want haar poes was te besig: You were born from your mother's arse, because her cunt was too busy.
Of course, there are variation on this, like Jy was uit jou ma se gat gebore want haar poes was te besig gewees om te naai vir geld daar by die docks: You were born from your mother's arse, because her cunt was too busy fucking for money there at the docks.
Not to mention the incomparable: Jou ma was nie genaai nie, jou pa het in haar poes gekak. Your mother wasn't fucked, your father shat in her cunt.
For simplicity Jou poes Your cunt is sometimes used. This is used indescrimately on males and females alike, in effect calling them a cunt.
gat is a generic word for a hole or pit and is often used in non-profane contexts to refer to indentations in the ground, but can also refer to the arsehole. It sometimes refers to the entire arse, as in Hy het op sy gat geval - He fell down on his arse.
Oddly, you never call someone a "gat", but you can call them a poephol "poop-hole" i.e. an arsehole.
Other epithets include moffie: Fairy, either in the context of wuss/wimp or of efiminate homosexual and Holnaaier: Arsefucker.
Thanks to frankie for the input.