I have Specialized Nimbus Armadillos and Specialized Thorn Resistant Tubes. Heavy and expensive but they seem pretty bullet proof. I crunched a big hunk of broken beer bottle at about 17mph with them a week or so ago (it was early morning and I just didn't see or react to it until it was too late). I heard the solid crunch and expected at least one flat but they took it in stride.

I am sure they are not bullet proof but I don't expect to get too many flats with them. I am prepared with spare tube, patch kit, pump , etc anyway, though.