Not 'use' because if you want to push a button on a wall and instead your guy catches the top of the wall and get killed... you are going to be mad.
Not 'walk' because it seems stupid to me, it is just to be slower, not really an action itself.
I'd say either crouch, or jump, but more like jump because you want to get higher by grabbing the edge.
By the way, not everybody uses WASD (almost you ll say, but no I don't, I actually use arrows to move, and numpad+Del,End,etc... for forcepowers, why? because I started like that in jk2, and I can't get used to anything else now, it's too late. And it's really good).