A fun hobby, and interesting to science.
I used to find them often as a boy in Florida. The banks of Hogtown Creek, which flows through the middle of Gainesville, abound with shark's teeth and other fossils. I've also found shark's teeth at the beaches of Rota, Spain.
Pic from the article:
The teeth I used to find at Hogtown Creek were usually in good shape, having just been washed out of the banks of the creek. They usually were polished like gemstones, and in the case of the Carcharodon teeth, they were razor-sharp. Biggest one I ever found was three inches long, shiny as a new penny, and I cut myself when I ran my finger along the edge of it. Wish I still had it.