Not that I'm condoning this in any way or anything
But making one that looks identical to a full stop would be even sneakier...
( elusive I'm not really here. You're imagining me, Mon 26 Jan 2009, 15:47, archived)

I was thinking about that just now.

( Dave Trouser ; the people's choice - 75% agree, Mon 26 Jan 2009, 15:55, archived)