Pretty much every mechanical object amazes me. When I begin to think of what these machines are made of (bits of metal, rubber, plastic, glass most of which are made from compounds of different elements which require certain bits of manufacturing to get in the first place) makes me feel just how useless I really am. Satellites are something that amaze me in particular. Sending things into space requires so many calculations. To manufacture a probe that is suitable for conditions far beyond those on Earth is an incredible acheivement. The amount of work spent on this for the interest of mankind is spellbinding. If you screw up on one thing then your spacecraft falls apart which will probably result in another 5 year gap until your next project. Sorry no pictures but you all know what I'm talking about anyway.