Captain Qwark commercial
Once you've beaten the game, wait for the credits to end to view a commercial featuring Captain Qwark.

Easy Bolts
After getting the metal detector, go back to previous planets and search for hidden Bolts. Not only does the metal detector help you find more, but the planets' items also respawn after you leave it.

Magnetic Wrench
Note: This also works with the Vacuum Gun. Execute a Comet Strike at far away Bolts. If the wrench passes near them, it will attract the Bolts to you. This is especially useful around water or Bolts that are across chasms.

Cheat mode
Defeat Drek, then perform one of the following combos at the "Goodies" menu to unlock the corresponding cheat option:

Temporary invincibility whenever health is full
Hit Comet-Strike(4), Flip Back, Full Second Crouch, Flip Back, Full Second Crouch, Comet-Strike(4).

Mirrored levels
Push Flip Left(4), 3-Hit Wrench Combo, Hyper Strike, Double Flip Right, Flip Right(2), Double Jump, Full Second Crouch.

Trippy trails
Push Wall Jump(10), Double Jump, Hyper-Strike.

Big head mode for Ratchet
Push Flip Back(3), Full Second Crouch, Stretch Jump, Full Second Glide.

Big head mode for Clank
Push Flip Back, Hyper-Strike, Comet-Strike, Double Jump, Hyper-Strike, Flip Left, Flip Right, Full Second Crouch.

Big head mode for enemies
Push Stretch Jump, Flip Back(3), Stretch Jump, Flip Back(3), Stretch Jump, Flip Back(3), Full Second Crouch.

Big head mode for NPCs
Push Flip Left, Flip Right, Flip Back(3), Comet-Strike, Double Jump, Comet-Strike, Hyper-Strike.