Fine, you won't get it anyway.

There's a room in Brinstar (might be Norfair, I forget), one with water and those snapping enemies you cannot kill, but you can freeze, along with a bunch of spikes.

Until you get the Gravity Suit you MUST turn off the High Jump or you can't jump up onto one of the platforms and thus carry on through the room.

There >_>

And by ability, I meant one of the powerups in the menu you equip not like, an equippable weapon-type like Missiles or Grapple Beam or X-Ray.