http://www.airbrushguru.com/airbrush...-airbrush.html
http://www.airbrushguru.com/airbrush...-airbrush.html
There are lots of brands I'm not hip to but you may be looking at a siphon feed style that has metal cups or the bottle option. Most siphon feeds come with both accessories and different sized tips.
http://www.google.com/imgres?q=paasc...9,r:1,s:0,i:76
Gravity feeds are a seperate animal and nothing changes out.
http://www.google.com/imgres?q=gravi...r:7,s:100,i:25
Ghetto airbrush, $9 single action just push the button and change the nozzle for a size of spray.
http://www.harborfreight.com/airbrush-kit-47791.html
In reality even a single action trigger I have seen people get some amazing effects that you wouldn't know was from a cheap air brush that had half an inch of paint on the outside of it. For some reason just pushing a button is no fun. double action, you push down the trigger and pull back and it regulates the paint pattern relative to how you move back. Lift the trigger and off. With a double action in one swipe with lots of practice you can start small, go big and taper down again in one stroke. A single action you keep stopping and adjusting the pattern until you like the size of the line. Screw with air pressure and thinning paint to get some effect.
I was just trying to narrow your search so you don't have to buy all of these like I did to figure out what worked for different things. Of course I did a lot of paying work but still I have about $600 worth of air brushes I never even touch. It is like an airbrush museum in my boxes.
Or you could do like Allen says and just buy one and start squirting paint and not worry about any of this. Damn him and being able to write one sentence and he's right.