I mostly carry an AirShip because it works with the 12g unthreaded cartridges. It's a little bigger than a threaded one (won't fit inside my seat bag, but carries nicely in the elastric strap on the bottom), but the 12g unthreaded cartridges are cheap enough to not sweat using them.

I also have a 16g threaded AirChuckSL that I love because its so small and light, but the cartridges cost a lot more. I only carry it when I really don't want to carry the heavy(er) AirShip. If I'm going to use threaded cartridges, this would be the only one I want. Tiny in size, and weighs almost nothing.

I think there may be a lighter 12g inflator somewhere... but I'm not really worried about it because the AirShip carries so well under my seat bag.