Great question PzJgr!!

On land I like Rommel, (surprise, surprise!) I don't think amyone did more with less. He commanded troop in France, shocked the British in North Africa, and had his "stop them on the beaches" policy been followed in Fortress Europe, D-Day would have been a disaster.

Sea, Carl Doernitz. He nearly brought England to surrender with just over 100 active, operational subs.

Air, I'm with you PzJgr, Hap Arnold because his daytime bombing tactics brought the Luftwaffe out to fight where it was destroyed.