Dig the zero-g pen ...

... in 2001: A Space Odyssey. To make Dr Heywood Floyd's pen float across the shuttle's interior, Kubrick's team stuck it on a piece of glass mounted on a rotating rig. The camera shoots straight through the glass and bingo - all you see is the pen. Of all the still-stunning effects in this SF classic, the zero-g pen's the one that really makes me smile.