While I like most entries, my favourites are LBGUI, Light Frog and FXED.
I would love to vote for all of them actually but I unhappily have to decide for one of them...

LBGUI: very boring to create, but very usefull stuff which is hopefully also easy to use, even though I didn´t really look into its integration.

Light Frog: I am not sure if it is well designed, but it basicly is, what the gamestudio template shaders are still missing: a pretty complete deferred shading pipeline. If it is easy to customize, it is basicly perfect and the shadow depth maps are great. Only problem of the shadows is the lightbleeding of the VSM...

FXED: a very complete shader editor. Only thing I really miss, is a more fixed layout with tabs. Other things which would make it perfect (maybe something of it is already possible?), would be the possibility to extend the editors keywords and the export format, by for example just adding some textfiles to some folder or something like that and support for more than one technique. Another problem of the editor, which actually makes it unhappily kinda useless, is that it doesn´t really allow "follow up effects", as you most of the time don´t just have one shader, but a several shaders and a lot of other code around them, which then finally results in the wished effect.
Also, with a pure textfile I have the feeling to have a better overview above everything.
What I basicly just want for writing shaders, is a good texteditor with hightlighting and automatic keyword proposals.

Hm, while writing this I finally decided for light frog now. In my opinion light frog and LBGUI deserve to win this .