Playing with randomness and how unrandom it can sometimes appear.
A drunk man starts at a lamp post at coordinates 0,0 and totters away for a walk of 1000 steps. Every step is randomly either north, south, east or west. You might expect that he'd stick pretty close to the lamp post, but press F9 and see where his walk gets him. It's surprising how purposeful randomness can appear. The red dot shows where he lands up after 1000 steps.
Download this Excel file and give it a go.