f7f18077_r_PlayStation_3___GameRankings__Unlockable
[How to Unlock] Solar Gun [Unlockable] 
Collect the five statues (those of the four Battle Beauties and the Frog Soldier/Haven Troopers in stage 1) using non-lethal means on their respective idols
Metal Gear Solid 4: Guns of the Patriots Cheats, Codes, and Secrets for PlayStation 3 - GameRankings