Among the ones you most commonly see in pet stores (at least my own experiences) are the Dwarf Puffer, which is a pure freshwater species, and the Green Spot Puffer and Figure 8 Puffer, which are both brackish.
One word of warning, puffers will not take any sort of flake food at all and many will not even eat frozen food...so if you want to have a puffer tank, be sure you have the ability and desire to provide a constant source of live food to them. I had a dwarf puffer tank a few years back and between snails and live bloodworms my guys were quite happy for a long time.
P.S. -- It's pretty easy to breed your own (pond) snails. Just get one of those white 5 gal plastic buckets from Home Depot or some place like that, fill it with water, and then throw all your scraps of your live aquarium plants in there. Or if you don't have a planted tank, just go to your nearest LFS and buy $10 bucks worth of some of their cheaper plants (something low light like Anacharis) and throw them in the bucket. Since pet stores consider pond snails a nuisance, you could probably just ask them to throw in a handful of pond snails with your plants, though even if you don't ask for that most LFS plants have snails and/or snail eggs on them anyways. Keep the bucket near enough to a window that it gets enough light to keep the plants alive, and before you know it you should have all sorts of snails in there. The snail poop will provide enough nutrients in the water column for the plants to grow, and the plants provide the food for the snails to live and breed. When you want to grab a snail or two to feed to your puffers, they are easy to find since the dark snails show up quite easily against the white walls of the bucket.
