what pump should I get?

Unless you're running a bike shop I'd imagine you are pretty unlikely to wear out a track pump. I have a Joe Blow and a SKS and they have both had years of use and been fine.

I've just had to change the o-ring on the SKS as it eventually perished so I'd look for a pump where you can get spares - both SKS and Topeak do rebuild kits for a few quid with replacement o-rings.

Edit: One thought not related to reliability - the biggest annoyance I find with track pumps is their bases. My SKS loves to fall over and my JB has a triangular base that whilst stable is very sharp edged, so likes to scratch the car boot at every opportunity. My advice, pay attention to the base!

To be honest I carry Co2 on group rides too, one of these as its tiny! http://www.wiggle.co.uk/lezyne-trigger-drive-inflator-with-co2-cartridge/

But I still carry a mini pump as a last resort, if you're really unlucky and get more than a couple of punctures or mess up getting the co2 into the tube etc - it's good to know you can always get home!

I have a Silca Pista track pump and to be honest wouldn't really recommend it. Now both the chuck and the gauge have been changed it's okay though - and the main part is serviceable, which the Topeak I had before and failed wasn't, so in the long run it might be a win.
Mini pump, I have a Race Rocket too, but I've only used it once.
(Road bike I have a Zefal frame pump (and a locking clip/mount thing for it), but frame pumps don't suit every bike/usage.)

Topeak race rocket - fits in a jersey pocket, light weight, has a flexible hose that extends out making it much more useable then most mini pumps. One word of caution - there is a MTB version which will not get road tyres upto a high enough pressure - make sure you buy the 160psi version and you'll actually be able to get a 700x23 tyre upto 100psi!

http://www.topeak.com/products/Pumps/racerocket_hpc_cb

I'd recommend my Airace Infinity Turbo floor pump. It works a dream, has the gauge at the top (with a useful indicator) and is very well built. Currently £30.77 on Amazon.

Lezyne Pressure Drive Mini (Medium size) gets a vote from me. Lovely bit of kit.

Be wary of the screw-on head types if your tubes have removable cores (which most seem to these days).

+1 for the Joe Blow range or the SKS Rennkompressor if you need to go higher than 120-160 psi (e.g. for a track bike).

The Joe blow track pumps are good, they have a few models at various price points, starting around £25 online. I have a sks kompressor, which is not pretty but goes on and on where others have failed. rrp. £50ish

Minipumps- I have used the topeak pocket rocket (about £16 on wiggle) and it was good. I now use the lezyne roaddrive (£34 CRC) which is very good.

Lezyne are as good as they get IMHO.

The floor pumps have a screw-on head that works much better than my Bontrager's rather ropey both-in-one schraeder/presta adapter while the Mini Drive pumps incorporate a tube like old-fashioned pumps. All are well made and nicely finished.

Topeak do some good ones too.