Unlock the billiards option by playing or practicing a full session of billiards in NefroNefroTown, Garland, or SimSim (Neuhafen Port).
Unlock Trot Battle
Fight in five or more arena fights or achieve a D rank to unlock the Trot Battle mode on the title screen.
Go to Fort Raven and dismount your Trot. There is a man near the entrance (walk there) who talks about the evils of trot machines. Agree or remain neutral and he will let you try out his new invention, the bicycle. After you finish the game or use the bicycle several times, return to him and make your argument. You can keep the bicycle if you agree or remain neutral. You can also simply not talk to the inventor again to keep your bicycle.
Submitted by simalcrum
Unlock Boomerang Arm (Unique)
At Skylark Farms East, there is a river that empties into a low cave. Enter with your trot vehicle to get to Garland Outskirts East. If you enter that map by the river cave, you find a chest with the Boomerang Arm (same one as Ginger's).
Unlock Throwing Arm (Unqiue)
Have a Normal Arm and a Steel Beam (commodity) in the inventory and head to the Killer Elephant Gang's base. Steel Beams are sold in Garland. Head to the GTW Company park point and speak to a big guy standing near a stack of beams. For the arm, speak to the first red gang member inside the base (he will be pointing at the giant trot next to another blue gang member) and he will offer to develop the Throwing Arm for 100 uroch.
Unlockable Drill Grill
You can buy the basic parts from various city trot shops. Have a Drill Arm and a Light Grill and develop it anywhere into the Drill Grill, which does damage during rams.
Unlockable Excalibur Arm (Unique)
You must choose to not to join the Bloody Mantis Gang to get this part. After the game is completed, visit Dandelion's workshop and speak with the assistant. This unlocks the door on 3F that leads to Dandelion's bat cave, complete with trot Batmobile. Examine the trot for the Excalibur and an uncommon grill frame.
Unlockable Six Wheel Legs
You can buy the basic parts at a city shop. Combine two three wheel frames for the six wheel frame.
Unlockable Spike Ball Arm
You can buy the basic parts from most city trot shops, except the Ball & Chain arm, which is from the Killer Elephant Gang base. Combine the Ball & Chain Arm with a Claw Arm for the Spike Ball Arm.
Unlockable Whip Arm (Unique)
You will need to assemble the Spiked Ball Arm first (see hint on this page). Buy a bolt of Silk (commodity) at Neuhafen's warehouse #3. Combine the Silk and Spike Ball Arm with the Desert Hornet engineer at the Hornet base. The engineer is sitting next to the base's stores (level above the trot garage).