Maximo vs. Army of Zin:
Rewards: 
If you would like to Master every stage, you will have to do the following: save all of the lives of the Innocents, find every one of the buried Treasure Chests (Secret Chests), collect every item in the stage (Koins, Diamonds, Armor... Everything, basically), and defeat every enemy in the stage (including those Evil Bunnies.) If an enemy falls off of the stage, it is counted as a kill. If you collect an item and die, you will have still collected the item. You will be rewarded with Art Galleries of concept images. 

Infinite Goodies: 
On Level 9, Down with the Ship, you have three minutes to destroy six reactors. Using the Drill Attack, you can destroy a reactor with three hits. Destroy five reactors, then spend the rest of your time fighting enemies. You can earn lots of money destroying enemies. When time is almost up, destroy the final reactor. Go back to Level 2. Purchase power-ups and continues from the merchant then save and quit the game. Load your save, return to Level 9 and repeat the tactic. You can do this as many times as you like and earn oodles of cash in the process.

Art Gallery 1 - Master "The First Strike"
Art Gallery 2 - Master "Into The Fire" 
Art Gallery 3 - Master "No Sanctuary"
Art Gallery 4 - Master "The House Crasher"
Art Gallery 5 - Master "Forest of Fear"
Art Gallery 6 - Master "Gallows Gorge"
Art Gallery 7 - Master "Sinister Stones"
Art Gallery 8 - Master "Cyclocks"
Art Gallery 9 - Master "Down With The Ship"
Art Gallery 10 - Master "Road To Hawkmoor"
Art Gallery 11 - Master "Perilous Path"
Art Gallery 12 - Master "The Under Hive"
Art Gallery 13 - Master "Old Wounds"
Art Gallery 14 - Master "The Great Vault"
Art Gallery 15 - Master "Drained Depths"
Art Gallery 16 - Master "Sunken City"
Art Gallery 17 - Master "Guardian of The Deep"
Art Gallery 18 - Master "The Soulcrusher"
Art Gallery 19 - Master "Tinker's Rescue"
Art Gallery 20 - Master "The Master Of The Zin"