Potassium Tetrabromoaurate(III) Crystals

Metallic gold was dissolved in a mixture of HBr and Br2 which was generated in-situ by addition of a small quantity of concentrated nitric acid to the hydrobromic acid. Once the gold dissolved the solution was evaporated and reconstituted with distilled water several times until these crystals emerged. 

Cadmium cyanide. This is made by combining saturated solutions of cadmium sulfate and an alkali cyanide. Cadmium cyanide precipitates out on mixing. It is photosensitive and decomposes to a brown substance rapidly even in indirect sunlight. However, low level white light that's sans UV seems to be OK. I don't know if it's UV light, intense white light, or both that cause the photodecomposition. Cadmium cyanide is nearly as toxic as thallium cyanide although so far as I am aware cadmium poisoning is treatable and you might even be able to have a somewhat normal life afterwards. Thallium is not so forgiving.

After multiple attempts I've finally succeeded in synthesizing thallium cyanide. The prep was not terribly efficient but nevertheless there it is. This is made by combining saturated solutions of thallium(I) nitrate and an alkali cyanide. Thallium cyanide precipitates out. It's best done with cold solutions. Thallium cyanide is not stable at high temps and will begin to decompose in a hot solution. Solid thallium cyanide breaks down when heated (probably to the monovalent oxide). It is not photosensitive. However, it's always a brownish color when it first precipitates. It turns white after sitting under the solution it precipitated from overnight.