Originally Posted by Photosmith

I'm surprised nobody mentioned the Schwalbe Marathon Plus yet. Since it has about a 10mm thick extra rubber layer in the tread, it has a much greater buffer zone when running over things like thorns and staples, which tend to stick in the tire then get hammered in deep as you continue to ride, unaware it is even in the tire. For comparison I logged 220 miles on stock Specialized non-Armadillo tires and got 3 flats. I switched to the Marathon plus tires and have only gotten 1 flat in 350 miles logged, and I've pulled at least two staples out which went a good 5-6mm deep in the tread but never penetrated the tube because of how thick the lining is. They're not perfect, if you run over a construction staple or a nail then you're still screwed, as all pneumatic tires have their limitations, but the SMP does offer probably the most meaningful fight against flats.

As for slime, I used it in one tube, and never again. It would goop up the filler valve any time I checked my tire pressure or added air, so after about 25 rides I couldn't even check the tire pressure anymore. At that point, it doesn't matter if it still holds air, it was so clogged up that it was effectively useless as a tire by then. I know many people swear by it, but I'd go airless before I went back to using slimed tubes again.