The only cyanide that is "deadly deadly" is hydrogen cyanide. The best poison for a story is the mercury based see: http://en.wikipedia....aren_Wetterhahn, dimethylmercury for which there is no cure! Perhaps eating castor beans from the bio lab? I like the cyanide idea. Maybe NaCN spilled on some generic acid, and then death by fumes. Drinking methanol? Or massive amounts of ethanol/ether? Dimethyformamide and a poison (cyanide again...)? All sorts of ways, I guess.