Somen Tchoyi scored a second half hat-trick as West Brom came from 3-0 down to salvage a draw at Newcastle.
Steven Taylor's scrappy finish from close-range had given Newcastle the lead before Peter Lovenkrands added a controversial second.
Jonas Olsson's 47th minute own goal appeared to seal West Brom's fate but the Baggies rallied in thrilling style.
Tchoyi slotted in his first and fired in a second before capping a superb comeback with an injury-time header.
It was an extraordinary end to a game that encapsulates both side's seasons.
West Brom, for so long in a relegation dogfight, lacked their usual verve in attack without Peter Odemwingie and Jerome Thomas, while Newcastle enjoyed a punchy start in what was expected to be a dead-rubber at St James's Park.
The decision to omit Odemwingie and Thomas appeared to be costly as Newcastle exerted their dominance in the early stages.
So it was no surprise when the Magpies took a 16th minute lead through centre-back Steven Taylor, who bagged his third goal in as many games.
West Brom failed to clear Ryan Taylor's inswinging corner and Steven Taylor, with his back to goal only three yards out, steered the ball into the net to open the scoring for the home side.
The visitors were forced into more defending when Shola Ameobi came close to doubling Newcastle's lead in the 32nd minute.
A casual clearance from Chris Brunt ricocheted off Joey Barton and into the path of Ameobi, who took the ball around Scott Carson and tried to squeeze his shot inside the near post - but Abdoulaye Meite got back just in time to clear.
Newcastle did not have to wait long until their dominance was rewarded with a second, though it came in controversial circumstances.
Lovenkrands's volley towards goal was palmed into the air by Carson, who scrambled back to prevent it going in before catching the ball on the goal-line.
The assistant referee immediately signalled for a goal but replays proved inconclusive as the call for goal-line technology will surely gather pace again.
West Brom, conscious of their need to try to pull one back before half time, crafted a couple of half chances and James Morrison came closest when he dragged Steven Taylor out of position with an intelligent first touch but fired his left-footed shot across the face of goal.
West Brom's hopes of a second half recovery were dented just two minutes after the break when a harmless cross from Jose Enrique on the left wing was turned into his own net by Olsson to give the home side what looked like an unassailable 3-0 lead.
But West Brom displayed the kind of character that has moved them away from the bottom three and into the safety of mid-table during Roy Hodgson's reign as manager.
Tchoyi, a handful to Newcastle all afternoon, timed his run perfectly to evade the home side's offside trap to slot the ball past Tim Krul and give West Brom what looked appeared little more than a consolation.
But Tchoyi scored another in the 71st minute when he found space at the far post, sidestepped Fabricio Coloccini rather easily, and fired into the roof of the net from close range to set up a finish that seemed almost impossible at half time.
Newcastle pushed to re-establish their two-goal cushion as Lovenkrands and Danny Guthrie both came close, but were unable to put the game to bed as Tchoyi became the hero with a dramatic late equaliser.
Olsson collected the ball on the left wing and crossed to the far post to Tchoyi, whose run had not been tracked.
The Cameroonian stooped low to head the ball home unchallenged from close-range before reeling away in elation.
West Brom, who have still never lost on the final day of a Premier League season, end their campaign in 11th while Newcastle are forced to settle for 12th.