I've been a Pinnacle Souveran Wax user since getting my first car in 1993 (a black Toyota truck). After using a variety of other waxes on the market (Zymol, Meguiar's, Mothers), I can say that there's nothing better on black or dark-colored cars. Many car care brands say they are the ultimate or the best, but this little-known brand really is.
When you use their entire system to prep your car (Body Shampoo, Paintwork Cleansing Lotion, Clay Bar) beforehand, you really end up with a finish that's worthy of Souveran. I'm told one of the key ingredients that makes Souveran so amazing is the high percentage of Brazilian Carnuba. The percentage in Souveran is higher than any other brand. Any higher would require the person applying it to melt it with their hand beforehand.
When applying the wax, you can feel the oils in the wax that penetrate the clearcoat to give it a rich, deep color. Many waxes also leave white residue on trim and in corners, but not Souveran. And there's no need to wait until it dries to wipe it off. With other waxes, this just causes white flakes. Not very desirable on that dark car of yours.
If you're looking to give Pinnacle a try, http://autogeek.net is an authorized reseller and can get you started.