Power
Thin Battery: Large length, 1/3 as much width, and very thin. Can be attached on all sides. About 1 or 2 needed to power a heavy-weight.
Extenders
Front Mountable Disc: Just like the DSL 4-mount discs, but the mounts are placed facing up rather that sideways. (Kinda like the stock RA2 discs.)
Size adjustable.
Spread Connector: Like a Y Connector, but with 2 extra mounts placed at an angle like the Y Connector to make something that looks kinda like the Eiffel Tower.
Motors
Rapid Swing Motor: (Don't know if possible to make) A burst motor that quickly fires from the start angle, to the finish angle, then equally powerfully back to the start angle, and repeats until you turn off the switch/stop holding down button.
Analog Burst Motor: (Don't know if possible to make) A burst motor that can fire in 2 directions, idle at the start angle, and fires at iether finish angle 1 or 2.
Differential Perm Motor: (Don't know if possible to make) EL 132 Perm Motor with a small flat and round differential on one of the mounting sides. The side with no differential spins in the direction assigned, and the side with the differential goes in the opposite direction.
Weapons
Saw: A rectangular saw, mountable on where the handle should be or on the opposing edge of the teeth. (Can be used with pneumatic parts to chew away damage, or strike with burst motors.)
Mobility
Special Caster: A balance caster, except only 2.5cm tall. It doesn't mount to the base, and instead, it mounts to any connector.
Skidding Wheel: Size adjustable wheels. Sizes depend on the motor. When put onto the corresponding motor and driven, the robot chassis will be extremely close the ground. (Assuming the motor is not raised.) Useful for getting under robots.
Extras
Attenae: A simple wire sticking out, like the ronin and typhoon decorations. Hopefully it can come in different colors.
Well that's all I can think of right now. I might add later. Thanks a bunch if some of these are added. :D