My jr high students liked playing "sculptionary" with plasticene clay - I came up with a list of words before hand, then each team had a sculptor come up and mold the clay to represent the word. No words, numbers, or throwing the clay allowed! Each team had to guess until someone got it right.
The other sculpture game I have used requires newspaper and tape; small groups or individuals compete to see who can make the tallest freestanding structure, or the one that can stick out the farthest from the edge of a table, in a limited period of time. I used this one to teach about the importance of knowing the possibilities and limitations of your medium.