What's a cheap (under $5) cool card you feel every collector should add to their collection?

       This question was recently posed by The Chronicles of Fuji.  I have seen it answered by a few blogs so I am gonna throw my answer hat into the ring (and horribly mix my metaphors).  I am a little torn whether to answer this with a favorite (selfishly) or with a universal truth kind of card (selflessly).  In an odd display for me, I will go with the latter and be selfless.

Obviously, I have also gone a bit vulgar.  This card needs no introduction.  It should be in every collection in one form or another.  I prefer the original naughty error version, but for the more demure of you, there is no end to the "corrected" variations.  I am lucky enough to have pulled one before the frenzy back in 1989, but since this card is from the height of the overproduced junk wax era, even this "rare" card is probably out there in the tens of thousands.  Some thought they might put their kids through college with one back in the day...these days, you can snag one off eBay for about $5.