This aluminium micro pump from Scott weighs a miniscule 88g, but it's still capable of pushing big, big pressures. The secret is a telescopic double barrel, which increases the volume of the stroke, while the narrow bore keeps the required force to a minimum. It took 225 strokes to hit 100psi, but it wasn't as much of a chore as with some of the others - though the barrel did get quite hot towards the end.
Rubber seals keep grime out of the head and barrel, and the barrel seal also holds the pump shut when it's stowed. Considering its size, the performance is excellent.