What is the fastest way to earn bolts?

Impossible challenge & arena battles work
also, use box breaker a lot

Just finish the game once, and try Challenge Mode new game, also don't forget to bring Armor Magnetizer and Box Breaker.

It's best to ignore the RYNO II and Zodiac in the first run through, then enter challenge mode. Run through most of this one, until you get to Planet Grelbin. After getting the tunnel open and the hypnomatic part, there will be 75 moonstones left, each one worth 30,000 bolts. This will get you over 2,000,000 bolts, more than enough to get the RYNO II.

1. Do either the Maktar Arena challenges or the Joba Arena challenges. (The Impossible Challenge especially because of the 200k reward)

2. On Planet Todano, once you pass the forest area (with the 4 rockets) and solve the electrolyzer puzzle at the end of the path, you see a platform go up and see what is front of you. A bridge that has around 20-30 destroyable scenery on it. With the Box Breaker smash all of the scenery on the bridge and you will end up with about 900 to 1250 bolts more. Simply die by jumping in the nearby water and repeat the procedure.

3. In space battles, pick any challenge where you have to kill X amount of spaceships. If you have the Nuke in your ship's quick select simply blast the nuke away and about 90% of the time all enemy ships will be vaporized. The challenges are #2 and #3 in the Feltzin System and challenge #2 on Planet Gorn (The Gorn challenge is recommended as it awards 2750 bolts upon completion after a certain number of times) (In other words, Do the Gorn challenge ten times and you'll get 27500 bolts.)

4. Collect crystals and moonstones. There are 90 crystals once you hand 10 over to the mystic so he can repair your ship and there is 75 moonstones on Planet Grelbin. The crystals are worth 1000 bolts and the moonstones are worth 3000 bolts.

5. Do the above 4 tricks in challenge mode because you'll be getting 10 times the bolts with the exception of Todano which only gives double the bolts (its scenery and in CM you only x2 bolts for destroying them)

Good luck.

1. Get the box breaker (see a walkthrough)
2. SMASH STUFF!