I use a Badger 400 touch up gun. I think this is the best one out there! I had a Chinese model and it did ok for a little while but the performance tapered off after awhile. The Badger sprays like a dream. All one has to do to keep this gun working like new is to clean it throughly each time you use it. I use PPG Concept paints, this paint line is so easy to use one can hardly mess it up. I have had it color matched to moneykote with no problems. The only drawback is the price, it is expensive! You can get the paint at auto paint outlets. Radio South also sells it in small quaintities that match moneykote.
Another paint gun that I think is a winner is the small gun that Porter Cable makes, I think the model number is #53. Lowes sells this gun for less than 60 dollars. It has the top gravity cup. the workmanship looks top notch.