It's only the middle of May, but already we've had some runaway viral hits in advertising this year. Unruly Media, which runs the global Viral Video Chart, has just released a list of the most-shared ads of 2012 (so far). We've posted the top 20 below. It's a varied group of spots—with dancing and singing, cursing and fainting, running and good old-fashioned pitching. President Obama even makes an appearance. Check out the full list after the jump. And don't resist the urge to share.