My friend's family lived in Tainan, so this was where we spent the most time--that is, two days. It is the best place to visit temples, though remember that the best ones are not on the main boulevards, but in alleyways. My friend tells me that due to new buildings sprouting all over the city in the last few years, they are increasingly harder to find on your own if you don't have a good map of Tainan.
One of my favorites, for I grew up with his legend, was the Kwankung Temple. It is located on Mintsu Road, opposite Chihkan tower, though the main entrance is in an alley way. Many travel guides will tell you that Kwankung is the saint of martial arts, revered for his physical strength. They would often contrast him with Confucius, who is the saint of literature. While it is true that Kwankung is associated with strength, his biggest appeal is that he is the symbol of loyalty, as he unhesitatingly agreed to a demand to exchange his life for his adopted brother's family. Many Chinese would light an incense to Kwankung before they would undertake tasks that require courage. Interestingly enough, Kwankung is also worshipped by many Chinese gangs. Like in every other Kwankung temple, Kwankung here is portrayed with a red face, a long beard, and in his hand, a long spear with a large sabre attached to the top (I am just not sure what we call it in English--anyone?). His statue is just huge here.