Bicycles

After walking would come bicycles. If you don't know how to ride a bicycle you should learn cause its one of those things that once you learn how you never forget. I learned when I was a small child and after I learned I spent half my life on a bicycle. Besides the fact its great exercise, its a lot of fun, and its 10 times faster than walking and the only problems you'll have is getting up a steep hill in which case you simply get off and walk (push) your bicycle up to the top of the hill and jump back on.
Bicycles come in all forms and shapes and sizes. There are mens bicycles, womens bicycles, and kids bicycles. Some come in the basic form and others have multiple speeds. On a good multispeed you can simply go to low and pedal right up a hill without haveing to get off and push as the lower the gear the easier it is to pedal.
There are even motorized bicycles. Some are electric but most are gasoline, driven by a small engine or motor mounted to drive either the front tire or the rear wheel. Most motorized bikes come in kit form consisting or the engine, fuel tank, and brackets and instructions to mount it with and rangeing in price from a couple hundred dollars to over 400 bucks, or if you are mechanically inclined you could build one yourself from spare parts.