Skipping Energy Controllers
Discovered by Anonymous and Maur
If you defeat a boss of a Dark Temple, but do not actually have Samus collect the energy within the temple's Energy Controller - those psychic barriers do not appear on the doors out of the area. This means that if you keep Samus from collecting the energy, you don't have to A) return it, or B) talk to U-Mos again. Sanctuary Fortress is the exception - you need to return the energy to make U-Mos give you the Light Suit.
In Dark Agon Temple, after you get the Dark Suit, turn around and head back to the entrance of the temple. Nullify the Light Crystal there with a normal dark beam shot, jump on top of the crystal, jump to the door, and go. For some reason the invisible platform above nullified light crystals is higher then that of regular light crystals... you can't make the jump without nullifying it.
[Mario123's note] The Sonic Pulse Emitters in Mining Plaza won't appear before you return the energy to Agon Wastes, making this part useless in a 100% run. From what I know, however, this is the only occurance. [A video clip shouldn't be required, but one would be nice.]
In Dark Torvus Temple, after you defeat Chykka, grab the Dark Visor. However, the elevator does not show up. You need to refresh the room in the game's memory to do this. Jump on the invisible platforms to the top and go through the door. Then, just head behind the bomb slot - that's right, behind it - which resets the room and allows you to leave without getting Torvus' energy. If the door back out to the Temple takes a while to open, then you've succeeded in refreshing the room! Head back out and take the elevator, forgetting about the energy.
Pity we can't skip the Sanctuary Fortress energy...
[Note from BroKeN:]