A couple of bricks

[zakmasood]

What brick would you like added? Include photos of a similar brick, or be specific in your description.
Here's a couple of bricks I would like to see!
A light emitting brick for lamps and such, being able to customize the color of the light as well.
A transparency slider, so we can adjust the value of the transparency as well of a brick.
A Hinge brick, so we can make DOORS!
Mechanical bricks, so we could make mock factories.
Why do we need this brick?