Bunn is highly valued at Sixfields and two unbelievable stops will have enhanced his worth, while leaving deflated Rovers boss Sean O'Driscoll shaking his head in disbelief.
Northampton were leading 1-0 when Gareth Roberts delivered a low cross into the path of the onrushing James Hayter in the 65th minute for a moment that had goal' written all over it. Hayter struck the ball perfectly, but somehow, Bunn not only saved the shot but held on to it.
The opening goal came in the 50th minute with Danny Jones delivering a low ball into the box, which allowed substitute Gilligan to execute a shot with the outside of his right boot, the ball looping up and over Neil Sullivan.
The first half had been sparse on chances although Mark Wilson had fired over the bar for the visitors when well placed in the fourth minute and the same player forced Bunn into a reaction save three minutes before the break.
Posed the question of chasing the game, Rovers stepped up a gear and enjoyed their best spell of the match with Mark McCammon foiled with a 55th minute header from a James O'Connor cross when he should have done better, before Bunn then made a brilliant full-stretch stop to push away a deflected drive by O'Connor.
Town had been beaten 2-0 at home by Rovers last season, but they fully redressed the balance in the 71st minute. Again, the goal stemmed from a cross by Jones and when Jason Crowe nodded the ball back into the danger zone, Andy Kirk scooped the ball up into the top corner.
Northampton could have added to their tally with a near-post header by Poul Hubertz, while Rovers knew it wasn't their night when substitute Paul Heffernan fired into the sidenetting a minute from time.