I'd say take a look at ropes, twists, plugs, cakes, and the like. A lot of them have a little higher nicotine. Virginias, Turkish and Orientals usually have higher sugar concentrations with lower nicotine than others. Fire cured, air cured and pressed and slightly fermented tobaccos have less sugar and more nicotine, usually. If you're looking for higher nicotine blends and you can search Smoking Pipes, there tobacco locator tool is priceless. It will allow you to search for the blends based on strength alone, if you choose.
As Cosmic stated above, not all of them can be pigeon-holed into one strength or another. Some Virginias are weak, some are strong, same for burleys.