A late goal from Neill Collins capped off an impressive performance as the Blades beat Turkish champions Fenerbahçe at Bramall Lane
In a friendly game which was staged to mark United's 125th anniversary, as well as raise funds for the Turkish Mining Disaster, 12,950 fans turned out.
Pierre Webó gave Fenerbahçe the lead in the first half but Chris Porter levelled with 15 minutes to goal before Collins won in on 90 minutes.
Flynn was named in the starting line-up for the first time this season, as was fellow Scot McNulty, whilst 17-year-old Reed was also included. New boy Wallace was on the bench for first time. Fenerbahçe's starting XI included Brazilian Diego, Portuguese duo Raul Meireles and Bruno Alves, as well as numerous Turkish internationals.
United began with Flynn and Davies in the full-back positions and had the best chance of the first 10 minutes when McNulty, four yards out, headed over a Davies corner. Fenerbahçe fired a warning shot through Meireles before taking the lead on 11 minutes. Erkin delivered a cross from the left and Webó's header was perfectly positioned beyond Howard's right arm.
Gönül half-volleyed over as Fenerbahçe kept possession, but the Blades went close on a number of occasions. Reed was blocked off when latching onto a Campbell-Ryce cross and McGahey's header from the resulting corner was saved at the near post by Demirel.
An acrobatic effort from Webó was saved by Howard as half-time approached, whilst the goalscorer also missed another good chance.
Early in the second period Howard was called upon again, saving from Sow from point-blank range and with Campbell-Ryce seeing a lot of the ball, the Blades were forcing the Turkish champions back - he delivered a cross for McNulty to head but substitute goalkeeper Günok saved.
United had a couple of penalty appeals turned down whilst Alcock replaced Flynn, who completed 55 minutes.
Howard saved from Diego after a neat turn by the Brazilian and then the Blades goalkeeper was down quickly to keep out a long-ranger from Sow.
Collins replaced McGahey and Doyle had an effort deflected wide before the Blades grabbed a deserved equaliser with 15 minutes remaining. Reed's lofted ball into the box found PORTER in space and the striker directed his header home.
It was Porter's final touch as he was one of four players substituted a minute later - Wallace was one of the players introduced for his debut, whilst trialist Crawford was also given another run out.
The Blades came close to a second on 82 minutes when Basham beat goalkeeper Günok to a Davies free-kick but the header was just wide
In the final ten minutes, youngster Dimaio replaced youngster Reed, who received a rousing reception from the Blades fans, but there was one final twist.
As the referee's watch ticked around to 90 minutes, an outswinging corner from Davies found COLLINS, who held off his marker and headed home from close range.
In injury-time McNulty had a chance to make it three before the final whistle marked a memorable win.
Blades: Howard, Flynn (Alcock 55), McGahey (Collins 68), Butler, Davies, Doyle (Basham 76), Reed (Dimaio 84), McGinn (Wallace 76), Porter (De Girolamo 76), Campbell-Ryce (Crawford 76), McNulty.
Unused: Willis, Harris, Murphy.
Fenerbahçe: Volkan Demirel, Bekir İrtegün, Mehmet Topal, Moussa Sow, Pierre Webó, Diego Ribas, Raul Meireles, Emre Belözoğlu, Bruno Alves, Gökhan Gönül, Caner Erkin.
Subs: Fehmi Mert Günok, Ertuğrul Taşkıran, Hasan Ali Kaldırım, Samuel Holmén, Berkay Can Değirmencioğlu, Cristian Baroni, Semih Ergül, Muhammed Akarslan, Selçuk Şahin, Michal Kadlec, Alper Potuk, Mehmet Topuz, Serdar Kesimal, Hakan Cinemre.