As wondered by Chris Tilling.
Like Loren Rosson III, I don't think I can narrow it down to just one, so I'll take four, in no particular order.
E P Sanders: A giant. Not always right, IMO, but always makes an impact.
Mark Goodacre and/or Michael Goulder: Do I have to pick just one of them? They may not have stopped the juggernaut just yet, but its pace has slowed and it looks to be coralled.
Paula Fredriksen: She may not be as prolific as a John Crossan, as well-published as a James H. Charlesworth, as diverse as a Joseph Fitzmyer or have made the impact of the other scholars I've mentioned, but she's right, IMHO, and that has to count for something.