The Sky Blues stormed fortress Windsor and grabbed the County Antrim Shield for the second time in four seasons, but Linfield's last trophy remains the 2014 Shield.
In November 2012, United stunned Linfield after winning a penalty shootout at The Oval so they have form when it comes to wrecking parties and it was the Blues who were hurting again last night.
After losing an Irish Cup final to Glenavon and League Cup decider to Cliftonville, the Sky Blues faithful feared another hard luck story but this time they had the last laugh.
Linfield were favourites to win this final but there aren't many predictable things in life and Irish League football consistently throws up surprises.
Paddy McNally headed United in front on 32 minutes but Guy Bates cancelled that out seven minutes into the second-half. It was Ferguson's troops, however, who produced a cutting edge in the second period with David Cushley netting in the 59th minute before Eoin Kane hit a third 17 minutes later.
Mark Stafford's header in the 85th minute sparked a tense final few minutes and Linfield struck the woodwork twice in injury-time but United held on.
Bates was promoted to Linfield's starting line-up for the suspended Paul Smyth while McNally filled the boots of the banned Johnny Taylor, both players paying a heavy price for dismissals in Saturday's Irish Cup battle.
United played three at the back and looked to push men forward but even though they were competitive in the opening half, they were fortunate to be in front at the interval.
Ferguson's men took their one clear chance in clinical fashion while the Blues had several opportunities.
In the seventh minute Bates' drive bounced off the chest of Jim Ervin and away to safety and on 16 minutes Jamie Mulgrew's piledriver shook the crossbar.
The Sky Blues made sporadic bursts forward but were restricted to long range efforts from Cushley. But they broke the deadlock in the 32nd minute when Tony Kane's free-kick gave McNally the chance to find the net with a superb downward header, the defender climbing above Mark Haughey.
In a lively start to the second-half, Waterworth blasted a shot over the bar while Gary Thompson's effort drifted wide of the post.
The first booking came in the 51st minute when Allan Jenkins was guilty of dissent after protesting at the awarding of a free-kick. A minute later, United conceded the equaliser when Niall Quinn's free-kick was flicked up into the air by keeper Alan Blayney and when the ball dropped, Bates hammered it home.
The Braidmen were on the canvas but they bounced straight back up again as Cushley's low, powerful drive in the 59th minute deflected off Stafford and flew past keeper Ross Glendinning.
The injured Matthew Clarke was replaced by Ross Gaynor and Aaron Burns came on for Quinn as Linfield reacted.
Blayney tipped over Jimmy Callacher's quickly taken set-piece before United scored a third. Eoin Kane was allowed to burst past Stafford in the penalty area and drill a shot into the roof of the net.
Linfield fought to the end and Stafford's header from Jonny Frazer's cross with five minutes remaining set up a nervous finale.
In the fourth minute of stoppage time, Kirk Millar's shot hammered against the crossbar and a minute later Burns struck the post.
A brave effort from Linfield but this was the Sky Blues' night.
The Ballymena United players are heroes - for more than one day.
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