How about this unique pen holder for your desk?
This requires very little work, really – the pen plastic holder piece can be found in places like Michaels, or you can just buy a cheap desktop holder and take it apart. The processor I’m using is an original Pentium Pro, which can be found on eBay for less than $20 (personally, I would have thought they would be cheaper nowadays), but any other processor can be used. The advantage of the Pentium Pro in this case is that it’s quite heavy and holds the pen nice and stable, but you can use any other CPU, and if it’s too light, you can just glue it to a piece of wood, glass or metal.
The next step is to just glue the pen holder to the processor, and you’re done!