The Zefal HPX is the most reliable pump you can buy but you have to learn to brace the head while using it to avoid presta valve damage. Schrader valves are less likely to be damaged but you still have to develop a bracing technique. Fewer parts = better. This pump is so reliable and fast you won't need a backup system like CO2. If you were stuck out in the middle of the high desert and had only one pump to save your life this this one you want.
Edit: The Zefal HPX still has an all metal head. The bracing technique I use is to curl the fingers of my left hand around the tire with two fingers on each side supporting the pump head then I put my the back of my left hand on the ground while holding the wheel and use my right arm to pump.
Last edited by Clem von Jones; 09-19-14 at 12:14 PM.