There is no Crystal Pistol unlock code for Nerf N-Strike on Wii. The weapon does not exist in that game.
Why the Confusion?
The Crystal Series (clear/translucent) blasters exist as physical Nerf toys (e.g., Crystal Maverick, Crystal Recon), not as in-game items for the Wii title.
Nerf N-Strike (Wii) unlocks are progression-based: complete missions, hit score targets, find hidden targets.
Actual Unlockables in the Game
Blasters: Deployer, Longstrike, Stampede, Vulcan, etc. (by completing stages).