I'm pretty fond of the Specialized Armadillos. They're big and heavy, like the gators, but I've pulled nails out of them and they kept holding air. There's also a lighter-weight folding bead version called the armadillo pro, which I'm given to understand is used as the go-to training tire for some pro teams. Those, too, I've pulled nails out of. And they don't weigh a ton.