Dyirbal

First it contains a sublanguage used when one's mother-in-law is present, called an avoidance language or mother-in-law language. The normal form of the language is called Guwal and the mother-in-law language is called Dyalnguy. There are fewer words in Dyalnguy; they are more generic: the grammar is the same.

Second it exhibits the rare phenomenon of syntactic ergativity. The description of it by the linguist Bob Dixon is an important work in linguistics, often quoted, because of the light it throws on ergativity, and syntax generally. Dyirbal is agglutinative, using suffixes but not prefixes, and has fairly free word order. Younger speakers, under the influence of English, are neglecting the ergative case.

Third, it has four noun classes. This is common enough in languages - German and Russian and Greek have three, Spanish and Italian two, Bantu languages many - but the distribution of nouns across the categories prompted the linguist George Lakoff to entitle a book Women, Fire, and Dangerous Things. (In French the moon is feminine and the sun is masculine: these lists don't really reveal much about the French or Dyirbal mind.) Here are the four classes listed by their article:

• Bayi: men, kangaroos, possums, bats, most snakes, most fishes, some birds, most insects, the moon, storms, rainbows, boomerangs, some spears, etc.
• Balan: women, anything connected with water or fire, bandicoots, dogs, platypus, echidna, some snakes, some fishes, most birds, fireflies, scorpions, crickets, the stars, shields, some spears, some trees, etc.
• Balam: all edible fruit and the plants that bear them, tubers, ferns, honey, cigarettes, wine, cake.
• Bala: parts of the body, meat, bees, wind, yamsticks, some spears, most trees, grass, mud, stones, noises, language, etc.

The article is used in front of any noun in a sentence: bayi yara baninyu 'the man came', balan dyugumbil baninyu 'the woman came'. The full declension of the article is:

            nominative  ergative  genitive  dative
masculine   bayi        banggul   bangul    bagul
feminine    balan       banggun   bangun    bagun
edible      balam       banggum   --        bagum
inanimate   bala        banggu    bangu     bagu

Nominative here can also be called absolutive.

As an example of the ergative, banggul yaranggu balan dyugumbil balgan 'the man-ERG hit the woman'. As an example of syntactic ergativity, with a man being the subject of an intransitive sentence and the object of a transitive sentence coordinated together, bayi yara baninyu banggun dyugumbiryu balgan 'the man came and the woman hit him'.

Some of this is from http://www.hku.hk/linguist/program/world8.html