The SRAM Mini Twist CO2 Inflator is a staff favorite because of its small size and simplicity. The small head makes it super easy to carry in a jersey pocket or seat bag. Just thread a cartridge on until it is punctured and then back it off to release the air. Air flow can be controlled by slightly tightening or loosening the cartridge. The minimalist will be content to carry only this inflator, a tube and a couple tire levers.
SRAM includes a generous 20 gram cartridge which is slightly more than you might need for a regular road bike so you will want to cut off the air flow once the pressure is up to 100-120psi. The extra air is good to have if a little leaks out and can be retained usually for a few days by screwing the head on tightly. The 20 gram size is perfect for a 29er mountain bike.
Restricted delivery - can only ship UPS ground within the continental U.S.