"Knight, Cavalier, Princess"
KCP is quite simply the greatest game ever... rather, it should be framed as such to encourage play. Have the group pair up and form a semi circle in front of you. Grab a volunteer and demonstrate the three different poses, encouraging the group to attempt each one. Once everyone is fairly well acquainted with the actions, yell out either Knight, Cavalier or Princess and then count down from 5. By the time you reach 0, everyone should be in the correct position.
Now, my technique is to build up the game as if it is a worldwide competition. I reference record breaking times and about how Bryan and I made it to the semi-finals only to be eliminated after stubbing a toe.
Incrementally decrease the count and vary up the pose selection. Never call people out, for although you said they *had* to complete the pose within a small amount of time, you never said there was a penalty for failure.
Get them down to a 1 second count, saying that this is semi-professional and most groups never make it this far... That always give a good bit of satisfaction when they actually find how fast they can complete the given pose.
Now what are the poses? Well, you'll have to buy my book! I'm just kidding, I don't have a book, although I will write one if anyone is yearning for more Pete! I'll post the poses tonight (hopefully) depending on whether I have a camera or not (at this moment, I do not).