Well, this isn't really an MOC per se, but I, like others around here, have felt LEGO was somewhat lacking when it came to the diversity of their medieval figs and factions (how many Lion and Dragon factions do we need?

). So, using only official LEGO parts (no customizing), I have assembled ~10 medieval factions which are both fantasy-based and more realistically-based. I also have ~10 "realistic"-looking knights and squires that might participate in a medieval tournament. Note that I said "assembled" and not "designed" as a lot of what I have comes more or less straight from official LEGO past product lines. Anyway, the point is that LEGO already has a lot for us fans to work with, as long as you know where to look, so hopefully my efforts will be somewhat helpful (esp. to those new to the hobby).
Here are a few samples:
I encourage you to check out the rest in my Brickshelf Gallery below
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=543598
Comments, questions, and criticisms welcome (in that order

)
Childhood: The flame that burns its brightest when we are least cognisant of it.