Stating the obvious.

There are three basic types of temples in Taiwan (Excluding explicitly Buddhist Monasteries, Christian Churches, and Muslim Mosques).
The first are female quasi-Buddhist temples (because Buddhism is associated with compassion and these deities are all compassionate).  The big ones are Matzu and Guanyin.  Matzu it the biggest single god cult in Taiwan.
The second type are Wen temples.  Wen means culture or literature, and by implication also means political office.  These includes Rua (Confucian Temples) and altars to Wenzi, Wen Chang, Wen ...etc....  People make sacrifices here when they want to do well on tests, and when they want a promotion (based on merit?), and perhaps when they have to confront corruption (I made that up, but it’s logical).
The third category of temples are those dedicated to Martial Gods.  These temples are by far the most numerous and probably the most diverse. These temples are absolutely covered floor to ceiling with elaborate carvings and images of fighters and battles legends and weapons.

But actually, Matzu and Guanyin always have fierce protectors with weapons around them, even if they aren’t on every wall.  And Wen Chang is always flanked by military figures too.

So here is the obvious: Martial arts is the religion of Chinese people. That wasn't obvious to me before visiting Taiwan.

God of Accounting! God of Accounting!

Back in San Francisco, most Chinese businesses have a statue of Guangong on an altar up high in the back of their stores, with offerings of incense and fruit.  He wears armor and carries a halbred, he has a red face and usually his liver is somewhat protruding to show his fierceness.

In Taiwan I learned that he is the god of accounting! The story goes that general Cao Cao (a very important figure in the spread of early Daoism) imprisoned General Guangong for a time.  During that time in prison, Guangong kept precise records of how much food he was given and upon his release he paid it back in full!   Thus, he is watching over the shop to make sure all transactions are accounted for!

For years I've been asking what this guy stands for, so just because I finally got a good answer, should not imply that your average shop keeper is going on the same information.  After all, martial gods are simply good for business.

On the floor of a business there is usually a smaller altar to Tudi, the god of the Earth, who is thought to be the first lease holder of any given business, thus some of his merit has accumulated on the spot.  It's kind of like if, a long time ago, there was a famous shop where your shop is today and perhaps someone (dead?) might come looking for their favorite (noodle? trinket?) shop--you could have some commemoration of that handy for them.  And hopefully still get their business.