(Whoa...this turned into a longer post than it was meant to be. Sorry.)
I second the anoles. In addition to green anoles, there are also Bahaman anoles, and I believe a few others that are commonly kept as pets.
Certain frogs are also great for 10 gallon aquariums.
Also, mourning geckos, if can find them, are great! They get to be about 3 inches, and you can successfully keep up to 6 in a ten gallon aquarium. They are, however, parthenogenic (
http://en.wikipedia.org/wiki/Parthenogenesis), which means they breed without the use of males (subsequently, all mourning geckos are females). You can remove the eggs when they are laid though. They are quite entertaining to watch. They will squish their tails at each other (the more you have in a smaller aquarium, the more territorial they will be) and their food and make a little clicking noise. They are, in many countries, an invasive species, and as such are able to withstand a wide range of conditions. They can be kept at room temperature as well, with a good misting in the morning. I have two of these and, as I said, they are very entertaining.
Another option may be pygmy chameleons. I don't know much about their care, but here is a site:
http://www.crestedlady.com/pygmycaresheet.htm. An aquarium, however, may not be the best enclosure for them.
Please, please, please do not get a turtle to keep in a ten gallon. Many people say you need ten gallons per inch of turtle. (I personally don't follow this very closely as I do maintenance on my turtle tanks two or three times a week and my turtles have plenty of swimming room.) You also need 2 or 3 times the amount of filtration you would need for fish. In a 20 gallon turtle tank, you would need a filter that's made for at least a 40 gallon tank. In my 55 gallon turtle tank, I have enough filtration for 130 gallons of water. In my other tank which has about 15 gallons of water, I have enough filtration for 40 gallons. Another thing to consider with a turtle tank is horizontal, not vertical, space is important. Turtles are very messy (messier than even goldfish).
Also, if you are considering getting in herp, and you live that far away from a pet store, you will probably want to order your live food online. This is much cheaper and you don't have to spend all that time and gas getting to the pet store.