He's impossible to buy for at the best of times so Christmas has wiped out the only idea I've had this year (fancy Bluetooth headphones). I think traditionally it's tin or aluminum with gems being diamond. He's into high end tech (that he buys when he wants it) and gaming (couple of very specific games he plays sporadically). He's not into "stuff" so there's no point getting him a thing for the sake of it (I got him a sound wave print of our wedding song one year, it's in a pile on his desk). All I can think of is cufflinks, which he does wear, but everything diamondesque is very blingy, which he's not.
Any ideas??