During your second playthrough (on Challenge Mode), you can purchase an item called the Golden Groovitron for 2,000,000 Raritanium.

In order to unlock the RYNO IV, you must first collect all of the pieces to the Gadgetron Holo-Plans, Bring them to the Smuggler, who will then build this device for you.

Once you’ve beaten the game, you can unlock Challenge Mode. This will allow you to play through the game again, but the enemies will be more difficult. However, weapons will max out at level ten instead of level five, giving you an added edge.