My favorite is Johnny. I like the size, which is a little above average (7" long X 1 3/4" diameter), and the realistic look/feel.
The Mustang is a close second, and has a couple of advantages. It doesn't have balls, so it works in more harnesses than Johnny does, and it's an average size (6 1/2" long X 1 1/2" diameter). FYI, the Mustang and Goodfella are VERY similar. The girth and details are the same, but the Goodfella has 360° balls which are designed to work with any harness and because of that, it's only 5 1/2" long.
The only one we don't like so far is the Maverick, because it's not as realistic as the other ones. But which one you'll like best depends on your size and realism preferences and how you're going to use it more than anything else.