A few ideas:
Darken
What
Similar to glow, Darken does just the opposite, making it darker.
Why
If we had glow and darken, then each color would really be 3 colors, with a normal, lighter, and darker variant. This allows gray and brown scales to have fewer colors and still have the same effect.
Water
What
Works like undulate, but applies the water effect.
Why
So you can use it without using events.
Wireframe
What
Makes the brick appear as wireframe without having building tools out.
Why
Would make for some interesting effects and whatever is necessary to make bricks appear wireframed already exists.
note:Might be better as a checkbox in the wrench menu
Ghost
What
Makes the brick appear as a coloured ghost brick
Why
Mainly for effect, would be interesting, and as above the necessary coding exists.
No Texture
What
Makes the brick be untextured-- no lines, no bumps, etc. Prints still show.
Why
Would be useful in many places and the lines can be annoying in some areas.
note:Might be better as a checkbox in the wrench menu. Should also still be able to have a secondary effect like undulate.