Of the many languages in Namibia, I am learning one called Thimbukushu. Thimbukushu is a Bantu language, making it one of the most complex on Earth. The Bantu languages I've heard so far (Otjiherero, Rukwangali) all have what's called a concord system. Basically all nouns are divided into semantic classes (a noun class for humans, a different noun class for animals, another noun class for household objects, etc). In Thimbukushu, there are 10 different noun classes, plus a special class for the gerund and infinitive form of verbs (the gerund and infinitive are identical in Thimbukushu). Depending on what class a noun is in, it will have different prefixes for singular and plural forms (for example, in the human class: maguva is one person, haguva is people). That much is simple enough, but the different classes also conjugate differently with verbs and adjectives. Basically, verbs and adjectives will adopt different prefixes depending on the class of the noun that they are operating on. I believe the different classes also have different possessive particles, also. I would give more specifics, but I'm still memorizing all the classes, and their concords, as the particles used in conjugation are called. Fortunately there are no exceptions to the rules, and all nouns can be put into classes based on their prefix (except for words borrowed from other languages).
However, as difficult as the system may seem, it has some interesting linguistic potential. For example, if you want to personify an animal, you can use the human noun class prefixes with that animal instead of the normal prefixes.
A really neat thing about Bantu languages is that they are phonetically very similar to Japanese. Actually, Japanese is a phonetic subset of Bantu languages, which means that Bantu language speakers make all the sounds that Japanese people make, and a few more (like nasals). I really like the way Thimbukushu sounds. The language flows well, and has a soothing tone. It also lacks any guttural sounds, which I am not a fan of.