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 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.
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. Get in the bomb slot in the security station and spin it. This will cause the game to dump the temple from memory so it can load the energy controller room. Spin the security station again (thus putting you back where you started) and enter the temple again. It's been refreshed - the elevator's now there! Hop in it and forget about the energy.
Pity we can't skip the Sanctuary Fortress energy...
