Ratchet & Clank Future: Tools of Destruction

Well just play through the game on Challenge mode and u should get vast amounts.

When you beat Captain Slag on Ublik's Passage, you will get the treasure mapper. This not only shows gold bolts and secret areas but also the location of raritanium crates.

Another way is to do the Gyro-cyle area on Rykan V once, jump into the lava and repeat. You can get around 1,000 raritanium each time you complete the routine.

Note* This works even better on challenge mode if you have a high multiplier

Another way is to purchase the mag-net launcher. This is the weapon with the most raritainium upgrades in the entire game. If you can earn enough raritanium to buy all of them then you will be in the zone!

I think the best place is the Nundac Asteroid Field on first time there. The crystals can only be broken once per run through. So every time when you have to find talwyn in the station, break the crystals.

There is really no easy way to do this!!

The only thing I can think of is to find one weapon that you like the most with max raritanium and play through the fight arena as many times as preferred. This is also a great way to get more gold and save up for the trillium armor found on challenge mode.