I'd say my Gen2 G19. It's size-efficient for the amount of ammo it carries, and it is controllable even when that ammo is +P+. G26 is a close second for much the same reason.
I'm also a fan of the .45GAP G37 - great hand fit and .45 caliber in one package. I wouldn't want to go to a shorter barrel in .45 (either GAP or ACP) due to the attendant loss in velocity and energy.
G19! Gen2! Great together!
Glock 17, 19, 21SF, 26, 37, 39
Glock Advanced Armorer (AA), Glock Instructor Workshop (IW)
Remington 870, Benelli M1, Smith & Wesson 3000, Mossberg 500