There are a lot of characters in the DC Universe who call each other best friends. It's one of the the aspects of the shared universe that brings fans back for more. But I've found that in every best friendship in the DCU, there are always three elements in common.
1)There is always some unifying theme between the best friends.
2)There is always a mix of different personalities between the friends.
3)There are usually distinct costume elements the characters have in common.
4)They have complimentary power sets and/or skill sets.
Here are some examples of what I'm talking about:
Their unifying theme is Light and Darkness. You could also say it's Powers vs No Powers. Clark is the more optimistic and trusting person, while Bruce is the realist who is slow to let anyone in. Costume-wise, their belts look similar. They both stomp around in boots and armor. They both have chest symbols. And they both have capes.
I could do three or four different versions of this one. Instead I'll go with Hal and Barry. Their unifying theme is Space and Time. You could say close range vs long range too. Both have a Fight AND Flight fighting style. Both have energy based powers. Hal is the West Coast, joker, flirt. Barry is the Midwestern, naive, straight-man. The have very simple form fitting costumes, no undies (ever), masks, and circular chest symbols.
Their unifying theme is Knight and Archer. One is liberal and the other is conservative. They're fantasy characters pulled into the present day. The both wear Green and have strong fantasy elements to their costumes.
Geoff Johns has stated that these New52 darlings will be best friends. Their unifying theme is Science and Magic. They're both very big guys. But they are still young. Cyborg is the role model superstar. Shazam is the bad boy joker. You can see a lot of Jack Kirby elements in their New 52 costumes. You can see similarities in their color schemes (red and white), they both have glowing chest symbols, they both have unique footwear, and they both have wrestler style belts.
Now we get to Wonder Woman. Who is or could be her best friend? Is there anyone with a complimentary costume, unifying theme, complimentary power set, and complimentary personality?