Best optical illusion EVER

http://blogs.discovermagazine.com/badastronomy/2009/06/24/the-blue-and-the-green/

I know... debates forum...

So, is this the Best optical illusion EVER, or what?

A similar theme, but more appropiate for this forum:

http://www.popularscience.co.uk/features/feat16.htm

Here's a memorable one.

http://illusioncontest.neuralcorrelate.com/2009/the-break-of-the-curveball/