The useless portal to dark world
From M2K2: Metroid Prime 2 Wiki
Discovered by: Several people
You can do a ghetto jump followed by a screw attack to reach the portal in the hall of honored dead. This is currently useless, but amusing.
this video shows reaching the portal
You can also reach the portal the first time you visit the room by using a BSJ or Floaty Jump. Vid (Outside link)