The Walter PP is a suppressed pistol available to George Brown in Commandos: Strike Force
The Spy's sidearm; the Walter PP has halved ammo capacity (2 magazines instead of 4 or 4 instead of 8 if on Easy difficulty.) but is the only suppressed firearm in Strike Force allowing him to quietly take out enemies with a single pistol shot to the head.
However it is the worst pistol in the game for a straight up fight, as it has the low damage of the Luger with the low capacity of the Colt and less overall ammo.
The PP can be obtained by Hawkins in A Cold Reception if the Spy trades it for a Luger and O'Brien can acquire it by hacking the game, the PP is the only pistol that O'Brien cannot dual wield.