Centre Eliota Fuimaono-Sapolu's interception try, converted by Freddie Burns, ensured the highest-scoring draw in Premiership history and the most points Leicester have ever conceded on home soil in a league game.
Tigers looked as though they would bounce back from their painful European exit to stay in charge of the Premiership title race but Fuimaono-Sapolu's score rewarded a battling performance from the Cherry and Whites.
Juggernaut wing Alesana Tuilagi scored three tries in 14 minutes to ruthlessly overturn an interval deficit, but Gloucester drew level at 34-34 before Leicester centre Billy Twelvetrees claimed what appeared to be a winning score midway through the final quarter.
Gloucester though, had other ideas, and the brilliant Fuimaono-Sapolu claimed his second try when he intercepted Jeremy Staunton's pass 60 metres out, which Burns goaled with the final kick of a 10-try thriller.
Third-placed Gloucester led 17-13 at the break following touchdowns from full-back Olly Morgan and Fuimaono-Sapolu, but Tuilagi then cut loose as he took his Premiership try tally this season to 10.
England fly-half Toby Flood converted Tuilagi's treble and also added the extras to an early Scott Hamilton score and Twelvetrees' touchdown, while two penalties meant he finished with 16 points.
Gloucester though, confirmed their status as probable play-off qualifiers, with flanker Andy Hazell and substitute centre Tim Molenaar adding second-half tries before Fuimaono-Sapolu and Burns provided the finishing touches.
Like Flood, Burns ended with 16 points, and Gloucester will feel disappointed that victory eluded them after stretching champions Leicester to the limit.
Bath 19-15 Harlequins
Springbok half-back duo Michael Claassens and Butch James scored all the points as Bath held on desperately to beat Harlequins 19-15 and leapfrog them into sixth place in the Aviva Premiership, boosting their hopes of Heineken Cup rugby next season.
The only try came after just 11 minutes as scrum-half Claassens finished one of the few fluent moves of a tension-racked game. James converted and kicked four penalties, missing just one kick.
All Harlequins points came from the boot of All Black fly-half Nick Evans.
Despite perfect windless conditions, it was clear both teams were hamstrung by the fear of missing out on the European bonanza next season and the match was dominated by the whistle of referee Dave Pearson.
But Bath's try came as Nick Abendanon made ground down the left and when the ball was swung right, Shontayne Hape glided through the Quins defence, found support from Ben Skirving and Claassens was on hand to finish off.
Exeter 12-33 Saracens
Saracens gained revenge for their defeat to Exeter at Vicarage Road back in October with a 33-12 victory - their seventh successive Aviva Premiership win.
The visitors dominated the final quarter and finished the game strongly, scoring 20 points to inflict the Chiefs' heaviest league defeat of the season.
Jason Shoemark scored the Chiefs' opening try and Sireli Naqelevuki added a consolation effort late on for the Devon side.
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