This was inspired by nicholasclewis's photo of his glowing Gold Star here: http://www.thingiverse.com/derivative:4360 . It really made me want to design a glowing, pointy, handheld object, especially since most of my designs aren't really meant to be handled. So, this is the result!
Thing10 is printed in two identical halves, which can be glued together to form a rough sphere, or enjoyed on their own. The printed half is vaguely reminiscent of the Sydney Opera House crossed with a sea urchin. I may have gotten carried away with the pointiness.
The walls are designed to be a single filament wide. I use 0.3mm layers, with width/thickness ratio of 2.0, giving a wall width of 0.6mm. If your wall width is different, you may want to scale the STL file. You probably want to preview the build in software, like with Skeinlayer in Skeinforge. In general, Skeinforge seems to be pretty finicky with very thin walls. I suggest printing multiple copies at the same time, like 2 or 4, to allow some cooling, since it is a very quick print.
If you are having trouble printing Thing10 at the default size, you could try scaling it up 2x (or whatever gives you double filament walls). I plan to try this soon since a big one would let you see the details better.
As for the glowing, options include fluorescent or glow-in-the-dark filament, or those types of paint applied afterwards. I designed Thing10 so it could be painted from the bottom (when printed in clear PLA), so that you don't rub off paint when playing with it. I used this technique with some glow-in-the-dark paint for the green one in the picture. The blue one is Ultimachine's translucent blue PLA. Obviously it is much easier to paint the two halves before gluing them together.
Thing 10: 35.7mm diameter x 15.66mm tall (each half)
Thing 10b: 71.4mm diameter x 31.31mm tall (each half)
I printed it out at double the size and it is much more impressive. I've uploaded Thing10b.stl which is just the original file linearly scaled by 2x. I recommend this larger version, and it is still pretty quick to print.