Most efficient pump?

The wind.

Flysurfer

Nuff said

bigger inflate valves is the answer.

I get probably 40-50 inflates off the Coleman (Walmart) pump by using the largest fitting and holding it against the inflate valve. If your kites have an inflate and deflate, hold it against the deflate plug for faster filling and less strain on the motor. It works.
The 2012 Fluid kites have the large intake (same valve Ozone uses) and it pumps MUCH easier than standard valves. All kites should have this type of valve.

Here's some info on Fluid Kites- http://kiteboardingtampabay.com/fluid-kites.html

Happy Kiting!
www.kiteboardingtampabay.com

Have a look at pumps 16 and 20

http://www.bolangcn.com/product_en.asp?cplb=Air%20Pump