Dupli color is some of the best paint I have ever worked with. It goes on incredibly smooth, and it covers very well. But it is expensive, and you can only get it at Autozone, Napa, Advanced Auto Parts, and stores like it.
My second choice would be rust oleum. I havn't really used it lately, but in the past it seemed to take a long time to dry, but after a week or so it wouldn't scratch or get any damage on it. Lowes usually has it.
I am not really familiar with krylon, I know that it goes on pretty well, and they usually have a lot of choices, and it is less expensive. But overall I am not sore how well it lasts. I know that walmart has a good color selection.