The hand steeple, where the fingers are making a little "roof top", is showing a lot of confidence. This hand gesture is very popular with lawyers, politicians and priests (it does resemble praying, don't you think?) and while it shows great confidence, you should not use it when you're trying to gain someone's trust... the hand steeple can make you look arrogant and schmug. It does show strength when negotiating.

The reverse hand steeple is similar to the hand steeple, but this gesture is used more often during listening, where the hand steeple is used more often during talking. And since women are better listeners than men, the reverse hand steeple is used more often by women.

People in leadership positions often hold their hands behind their back... it's a pose that shows power, and confidence, as it exposes the vulnerable parts of the body. It also improves your posture and opens up the air ways, so you gain more energy and feel more confident as you do this.
Some people don't hold their hands but have one hand hold the wrist or the arm. This is a sign of frustration. The higher up the hand is, the more frustrated. It's a way to 'get a grip' on yourself.

Another show of confidence and feeling superior is by showing the thumbs. It could be as shown here, but any position where the thumbs are visible will do the trick. Holding your jacket with your thumb up, or have them stuck out of your back pockets are similar hand gestures that will do the trick.

Presenting your head on your hands is a way of showing that you're ready to move forward. Works great when flirting during a dinner date!

Another posture that reveals the vulnerable parts of the body, while opening up the airways (similar to holding your hands on your back), is by putting your hands behind your head. You also use more room this way, a sign that you are an extraverted, confident, outgoing person.

While not really appropriate for civilians, I do feel that the Military Salute is showing a lot of confidence. A straignt hand, sharp movement to the temple, does show that "consider it done" kind of confidence. As such, I really wanted to add this... as I do have a lot of respect for the men and women who serve and defend, while putting their own life on the line!