I buy Specialized red packet which I carry with me on FNRttCs, not just for my own use, but for any puncturee that I happen to be near
- I've never ever had one fail (other than when I've not seated the tyre correctly), and, considering that I've used a dozen a year on my bike and on other bikes for the last four years isn't bad going
- they're light
- they're pre-talced which makes getting them on easier, particularly if it's cold, dark, wet and you're not at your best.
on the downside they are expensive. I get a deal on the price, but you're probably looking at five or six quid most of the time.