I don't think you quite understand how metal detectors work. Yes, you can turn them on and detect every piece of metal there is to find, and you can end up digging a world-full of trash out of the ground. Like most anything else, it takes time and experience to become pretty good with a detector.
Also, different detectors have different purposes. Pinpointers are just that - they're used for VERY short-distance metal detecting. They help prevent unnecessary digging, which helps to prevent excessive damage to turf.
There are detectors with digital displays and those with nothing but a single tone. Both will detect metal. Some detectors are not meant for going more than 3-5 inches down. Those would be in the entry-level category.
I'm not trying to turn you off of metal detecting, but rather to show how there's more to it than just picking one up, turning it on and then being able to dig up all these goodies that you couldn't otherwise see. It usually takes about 100 hours of use, on average, for someone to learn to understand the language their detector is speaking to them. It usually takes longer than that to become really good - able to detect down 7" and deeper, without digging up a barrel full of trash as well.
I would recommend Bigfoot's suggestion.
www.TheRingFinders.com or
www.ILostMyStuff.com should be able to help you. They could also probably give you some quick help on getting started with your own metal detector, or help with choosing the right model.
There are lots of posts on Tnet about choosing the right detector, as well as tons of tips for using them to their fullest capacity. You can click on Forum in the upper left corner to see all the different categories, or can also type search words into the search box in the upper right corner.
Good luck and happy hunting!