Ratchet & Clank: Size Matters Cheats

Unlockable skins
Go to the Specials under the pause menu, then toggle them on or off:

Plundering Pirate Captain Skin: 6 Titanium Bolts
Ratchetzilla Skin: 6 Titanium Bolts
Troical Vacation Skin: 4 Titanium Bolts

Infinite Bolts
In order to attempt this technique to acquire infinite bolts, you'll need the following: Box Breaker, Map-o-Matic, Polarizer, Static Barrier, and Hyper Shot. You'll also need to have beaten the game at least one time (so that you have the multiplier). If you have all of that, then follow the directions below to score infinite bolts.

1) After saving Ratchet from the Medical Outpost Omega, head back to Metalis, and use the Polarizer to open the door that leads to a secret area. Head into the secret area and grab the Titanium Bolt.
2) You will now need to max out your bolt multiplier in order to be successful. Head to Pokitaru and replay the level, keeping your Static Barrier up so that you won't sustain injury (if you get injured, the multiplier will be reset). When you're done, you should have a x12 multiplier, which is the maximum attainable multiplier after beating the game once through.
3) Once maxed out, keep it that way and go back to Metalis. Use the teleporter to go to the arena where the titanium bolt previously was. Stand in the middle of the ring of boxes and perform a Hyper Strike. This should break the box - more will break all the boxes. With the bolt multiplier engaged, you should now have about 400,000 more bolts than before. Save the game without battling enemies, and load the game again, repeating this step over and over again as desired.