I'll agree on Pt. Assessment. IF you can't do it right, then everything else is useless. You can backboard, give meds, aed, etc... but if you can't quickly identify the need for these procedures then what's the point?
However, I get the feeling that a joke is coming, so.... The greatest skill learned was how to drive code with one hand on the siren, one hand on my burger, and the combination of my elbow and knee driving the rig. Obviouslty there is great need to get the rest of the burger down before we go on scene! ^_^ just kidding, before anyone starts ranting about safe driving.