Hawaiian hand gesture. It has many meanings. Originally it means to "hang loose", or to chill and be laid back. It can be used as a positive reinforcement. If somebody did something good, cool, or righteous; You can give them a shaka as a sign of approval or praise. It can also be used as a welcome/goodbye sign. Most people would give the shaka as a sign of wassup or hello, use it as a way of saying goodbye, and even use it as a thank you.
To make a shaka:
1. make a fist (not a tight fist)
2. extend both your pinky and your thumb.
3. lightly shake your hand (too fast makes you like retarded or like a tourist, and too slow make you look stupid.)
4. If you don't want to do the shake, you are also able to do the "I'm tuff" motion. In a downward motion, move your hand. Giving a kind of downward wrist flick at the end. It gives you a more "i'm bad look". It's mainly used by old school Local boyz.
One of the worst actors every to grace the screen. Every single one of his roles is exactly the same, the charming moron. Girls like him because he's famous. Girls like Kid Rock because he's famous too. Does that say anything?