i have a toppeak two timer, pump and co2 inflater in one, moves enough air to put 40 psi in a mtn bike tire (who runs that much anyway?????) and you can carry Co2 for inflating even faster (i usually do, but didnt want to be stranded if the CO2 didnt work for some reason)
I had many chances to try the new Blackburn Air Stick Long neck this week.
It looks hokey as hell but it works really well. I never flatted personally but I let many people use it and everyone commented that it was a super pump.
It is a dual stage with a hose that keeps you from torquing the valve when you are pumping. Lifetime warranty too.
It has high and low volume settings which is a great feature.
It is technically a road pump but it works great, even with big volume 29er tires..
The longneck like J mentioned or the Lezyne pumps are the best. I have a topeak mtn rocket that I carry on group rides. I have never had to use it myself on the trail, but everyone who uses it says its the best hand pump they have used.
A few days ago I bought a CrankBros. dual head pump( Presta & Schraeder) so that I could bring just one pump when me & the wifey hits the trail. She having the Schraeder valves & me with the Presta. I'm still trying to get used to it since you have to twist the head to lock it into the valve & I'm not used to it.