Humans

First off, sorry.  Pokemon has taken over my life, blah blah blah.  On to the challenge.

Humans are my favorite humanoid.  A) everyone knows what they are.  B) they are endlessly mutable.  C) extra feats and skill points (in D20 systems) are great.  And D) it's easy to slip into a "human" mindset, because I already have one.  Need random townsfolk or a horrifying cult?  Got it.  Humans are the baseline by which all other races are measured, therefore they're overlooked often.  As with other overlooked things (i.e. cats), I like using them to blow peoples' minds.  

Seriously, who is going to pay attention to the guy on the end?

One of my favorite tricks with humans is in a setting with a hidden bad guy and several possibilities as to who it could be, for example, a high council.  Describe everyone the exact same, just point out races.  It's a guarantee that the human is the second to last one the players will suspect (after the Aasimar).  But anyways, this is a short post, because there's not much else for me to bring to the table.