Town were hoping to finish with a flourish with a seventh successive victory which would have taken them to a club record 100 points.
But last year's third division champions refused to play second fiddle in a cracking six-goal thriller.
Rovers caught Luton napping at the start when they snatched the lead after just 28 seconds following clever play from midfield ace John Doolan.
James Coppinger produced the final cross and Guy fired home via the post at the second attempt.
Doncaster were the better side in the first half despite playing into a gale force wind but Dave Mulligan and Michael McIndoe both missed chances to increase the lead.
They had cause for regret when Russell Perrett equalised with a splendid header following a 32nd minute free-kick.
The champions forged ahead three minutes later when top-scorer Steven Howard cashed in on a goalkeeping blunder to notch his 22nd goal of the season.
Doncaster hit back again to equalise in the 51st minute when Luton midfielder Steve Robinson had the misfortune to turn a cross from Leo Fortune-West into his own goal.
Town skipper Kevin Nicholls scored with a magnificent 25-yard strike to put Luton 3-2 in front in the 63rd minute, but the home side refused to lie down and Guy struck again two minutes later to earn Rovers a deserved point following good work by Paul Green.
Both sides missed chances to win the match in the closing stages but a draw was a fair result overall.