Mine is the Speed Booster.

The Space Jump. I like how you can basically fly.

Do you think the Screw Attack from the second and third Prime games would count as "Other" or "Screw Attack"? Since it sort of has the Wall Jump implimented into it and has the ability to take you along some larger gaps whereas it seems that only its 2D characteristics are listed above in the poll.
Mind you, now I think about it, it's still called Screw Attack, right? I'm going for Screw Attack then, purely because the Prime style Screw Attack rocks. ^_^

Well, yes the 3-D Screw Attacks count as a Screw Attack regardless if they are a little different.