Metal Gear Solid 4

"Metal Gear Solid 4 Solar Gun
There are specific conditions to unlocking the Solar Gun secret item in Metal Gear Solid 4. You need to collect 5 secret dolls hidden throughout the game:
the Frog Soldier Doll,
Laughing Octopus Doll,
Raging Raven Doll,
Crying Wolf Doll,
and the Screaming Mantis Doll.
The secret dolls are acquired by defeating certain sections and bosses by using all non-lethal attacks, such as tranquilizer darts. The Solar Gun, once acquired on a second playthrough, can be charged up and fired upon enemy soldiers, knocking them unconscious and making them drop choice items"

http://www.mahalo.com/metal-gear-solid-4-unlockables/

"1-defeat the frogs in act i using nonlethal weapons (mk2,M870 V-RING AMMO,mosin negant).Then collect their statue/doll when meryl team leave,it is in the garage right after you resume playing.
2-defeat the laughing octopus THE BEAST FORM w nonlethal weapons,(M870 is the best here) then get the doll during the beauty fight on one of the beds,don't kill HER just deplete her stamina.
3-Defeat raging raven using nonlethal weapons the beast form then collect the doll on the rooftop during the beauty fight then use any nonlethal wp to finish her stamina.
4-defeat crying wolf using nonlethal weapons the best strategy is going under the truck and activate the N/V and keep sniping her with mosin negant it will take about 15 minutes so be patieint.Then take her doll by hugging the wall and searching during the beauty fight and you should spot the doll,after that finish the beauty's stamina.
5-defeat screaming mantis normally (using her mantis puppet) then during the beauty fight you will find the doll in the corridor you entered from then finish her stamina again"

http://www.gamefaqs.com/ps3/926596-metal-gear-solid-4-guns-of-the-patriots/answers?qid=33730

Eli vain tiettyjä, eikä koko peliä.

Täytyy myös jokaisen pomon jälkeen kerätä pieni piilotettu nukke, mutta ne on aika helposti löydettävissä.