After my previous BikeHut hand pump only lasted about a month and failed on second use, I decided to buy the best small pump I could find. All the reviews led me to Lezyne.
I purchased the Lezyne Alloy Drive high-volume pump in Medium size. See http://www.lezyne.com/alloy-drive for all the details.
The pump is extremely light at only 128 grams and is small enough to carry in your Camelbak, although probably better with the small size if you're going to carry it - 166mm vs 214mm long. I mounted mine on the frame with the supplied cradle. The cradle is designed to fit under a bottle holder, so it sticks out to one side.
This pump is pure class and oozes quality - it's 100% aluminium. The flexible hose is double ended for either presta or schrader valves, yet cleverly also screws into the pump either way. As this is the high-volume version, which is ideal for mountain bikes, it inflates a standard 26x2.1" tube in less than a minute.
At both ends of the pump are rubber caps protecting the pump from dirt and water. I found that these aren't quite secure enough and don't offer enough protection if the pump is mounted on the lower section of the frame where it gets covered in crud. So I've resorted to wrapping the pump in a plastic bag, which spoils the look a little, but at least is stops grit getting into the threads.
At £23.88 delivered (of an eBay retailer), this pump is well worth the money, considering that my previous pump cost £20 and only lasted a month before the seals failed. I normally get a puncture on every weekend ride and I find this pump a pleasure to use. I'd go so far as to say it is perfect and unbeatable. I just wish there was a little protective jacket for it, as it's too nice to get dirty!
My rating: 10/10