The former Manchester United man, who had been dropped for the past two games, hit an injury-time winner as the Pilgrims came from behind to move back into the Championship play-off places.
The 90 minutes were up when Ebanks-Blake was first to react after team-mate Krisztian Timar's effort had hit the bar.
Rangers went ahead when Timar's Hungarian compatriot Akos Buzsaky, who is on loan to Rangers from Argyle, began the move that led to Rowan Vine's opener midway through the first half.
Buzsaky's optimistic pass to Martin Rowlands became a good choice when defender Paul Connolly's slip allowed the winger to pull back a cross from the byline.
The ball went all the way across the face of the goal to the far post, where Vine applied the finishing touch.
Argyle finished the half strongly and emerged for the second half in a similar frame of mind and Halmosi won a penalty from which Argyle levelled.
After diving in between Adam Bolder and Gareth Ainsworth, Halmosi's shot struck Rowlands on the arm and Ebanks-Blake fired the resultant spot-kick home low and powerfully.
QPR finished strongly and substitute Dexter Blackstock, a former Plymouth loan player, should have done better than head a corner straight at Argyle goalkeeper Romain Larrieu.
Argyle looked to have wasted their chance of a winner when a Halmosi corner, just before the 90 minutes was up, went all the way across the goal.
Then up popped Ebanks-Blake for his 11th goal of the season for an emotional end to the game.
There was still time for referee Steve Bratt to send off Mikele Leigertwood after the final whistle.