Steak and kidney, especially as one of those boil-in-the-tin things. Closely one-upped by either chicken and mushroom, a pasty (if they count) or a Greggs Steak Bake / Ginsters slice (pretty much any of them except the lacklustre cheese & ham) which push the very definition of a pie, but it's my vote so I say they make the cut.
What's with all you sugar junkies, honestly. Pie already has an enormous carb hit, you want to pile sucrose/fructose/glucose into the mix as well? Balance it with some goddamn protein! Plus the gooey layer of pastry between the dry part and the filling goes much better with savoury fills.
Though I'll admit a soft spot for a really good apple and blackcurrant with lots of custard.
Now, if cheesecake may vaguely count as a pie, what about quiche? Or trifle?