Nathan Jarman hit the winner for Grimsby as they condemned Coca-Cola League Two leaders Wycombe to their first home defeat of the league campaign.
Wanderers had not lost a league match at Adams Park since February 2008 but found themselves behind after 23 minutes when Jarman hit Jean-Louis Akpa Akpro's cross first time past home stopper Scott Shearer.
Darlington moved into third after putting bottom side Luton to the sword with a 5-1 thrashing at the Balfour Webnet Darlington Arena.
Robert Purdie followed up his 10th-minute penalty with a 24th-minute header before Liam Hatch's free-kick made it 3-0.
Neil Austin then added a fourth before Chris Martin hit back with a left-foot strike for Luton.
Gregg Blundell added further misery to Mick Harford's men when he picked up a fifth five minutes from time.
Bradford slipped to fourth after being held 1-1 by Accrington at Valley Parade.
Barry Conlon equalised James Ryan's free-kick but the Bantams could not find a winner and are now level on points with Darlington.
Mark Phillips' last-minute goal rescued a point for Brentford against Notts County at Griffin Park. Nathan Elder's foul on Mike Edwards earned him a red card before Delroy Facey put County ahead.
County looked set for their fourth away win of the season before Phillips denied them all three points with a close-range header.
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