The WWR JDF Mighty Square is a Good Smile Company exclusive. This is the largest Square, and is of the Japan Defense Force colorway. This larger size allows for a little side door that opens to reveal the Square's guts.
It will be available to pre-order beginning on February 12th 2012 at 5:00PM JST for ¥12,600 plus ¥2,000 for shipping (about $190 total). The sale will run until February 20th 2012 at 9:00PM JST. Look for them to be mailed out around June 2012.