Ondrej Celustka fired home a famous 76th-minute winner as Turkish substitutes Trabzonspor stunned Inter Milan in their Champions League Group D opener at the San Siro.
The Turkish side are only in the tournament because Fenerbahce were kicked out due to match-rigging allegations and they seized their chance when Celustka swept home the rebound after Halil Altintop's shot rebounded off the woodwork.
The 1-0 defeat was a stunning setback for the 2010 champions who had dominated much of the evening with Mauro Zarate having the pick of the chances before they paid for their failure in front of goal.
In another dramatic Group D clash, Spartak Moscow hit back from 2-0 down to draw 2-2 with Lille in France. Seydou Doumbia scored twice - his second in injury time - to cancel out strikes from Moussa Sow and Benoit Pedretti.
Ryan Giggs rolled back the years to rescue last season's beaten finalists Manchester United a point in their opening Group C clash against Benfica at the Stadium of Light.
Giggs drilled home a magnificent 42nd-minute equaliser in the Stadium of Light after Oscar Cardozo had turned Jonny Evans in the box and given the Portuguese side a 24th-minute lead.
It was a sluggish performance from United but the point will have pleased boss Sir Alex Ferguson who made eight changes - including replacing keeper David De Gea with one eye on Sunday's clash with Chelsea.
Also in Group C, an Alexander Frei penalty six minutes from time gave Swiss side Basle a 2-1 win over Romanian Champions League debutants Otelul Galati in match which saw two red cards.
Fabian Frei's 39th-minute effort put Basle up at the break before Marius Pena's 58th minute equaliser. Adrian Salagean was sent off shortly before Frei's winner, and Basle's Benjamin Huggel followed two minutes from time.
Like United, Manchester City also had to come from behind to ensure their Champions League debut did not end in defeat against Napoli at the City of Manchester Stadium.
After both sides struck the woodwork in the first half - City's Yaya Toure and Ezequiel Lavezzi for the visitors - Edison Cavani silenced the home crowd by putting Napoli ahead on 69.
But five minutes later Roberto Mancini's men drew level when Aleksandar Kolarov blasted home direct from a free-kick. City's Vincent Kompany also cleared off the line to deny Marek Hamsik.
Group A rivals Bayern Munich showed they mean business with a 2-0 win in Spain over Villarreal. Toni Kroos set the Germans on their way after just seven minutes and Brazilian Rafina wrapped up victory 14 minutes from time.
Real Madrid made do without suspended coach Jose Mourinho and injured midfielder Kaka as they started their campaign in Group D by nudging past Dinamo Zagreb 1-0 in Croatia.
Angel di Maria struck the all-important goal in the 53rd minute but it was far from plain sailing for the Spanish giants, who survived with 10 men for last 18 minutes after Marcelo's dismissal for a second yellow card.
Also in Group D, Ajax and Lyon played out a dull goalless draw in Amsterdam, with the dangerous Michel Bastos coming closest to winning it for the French side.