I've always wanted to do the king. I mean come on "wake up with the king." the costume writes its own pickup lines! However one of my prerequisites is that I have to be able to easily drink in my costume. I couldnt figure that one out.
Other Ideas I've had:
Toga - easy, cheap, generic
Price is Right Contestant - easy, cheap
My costume (cant give my idea away! It'll be stolen
)
Those old fully green army men figurines (with the plastic feet)
One thing I used to do in years past was search the picture section on Collegehumor.com.