Topeak JoeBlow Sport III Floor Pump
This is the pump we use in the shop - it's extremely durable. It has a twin head, with one side for Schrader (car) valves, and the other side for Presta/Woods valves. This means the rubber seals last longer than one-size-fits-all pump heads.
It also has a couple of head fittings for pumping up balls and air mattresses.
If you buy one bicycle accessory, it should be a pump. And it should be this pump. Highly recommended.