France snatched victory with a last-gasp Dimitri Payet free kick but it was Coman who caught the eye as the 19-year-old Bayern Munich winger set up a goal and made his presence felt all over the pitch until he came off in the 77th minute.
His performance confirmed that the hosts can bank on young talent up front in the June 10-July 10 tournament.
France opened the scoring after 20 minutes in the western port city when midfielder Blaise Matuidi volleyed home a fine cross by Coman, starting a match for France for the first time.
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Cameroon levelled two minutes later, Vincent Aboubacar catching the home defence off guard to tap in from close range.
Striker Olivier Giroud put the hosts ahead from a Paul Pogba cross four minutes before the break.
The second half proved relatively uneventful until Eric Choupo Moting equalised from close range two minutes from time before Payet popped up with the winner at the death.
DEFENSIVE WOES
France boast a string of impressive forwards and fine midfielders but have been hampered by defensive woes in their build-up to the finals.
Versatile defender Jeremy Mathieu and centre-back Raphael Varane have been ruled out of the tournament with injuries.
Their backline, with Laurent Koscielny and Adil Rami paired in central defence for the first time in four years, looked shaky against a determined Cameroon side and must clearly be France coach Didier Deschamps's main concern.
"Everything was not perfect but at least the spirit we need was there and that's the most important thing", said Deschamps, who learned his trade with Nantes before captaining France to their 1998 World Cup and Euro 2000 triumphs.
"We have things to work on, it's true, but we have a group of players and all them know they can play a role," he told French television channel TF1.
Deschamps, who has until Tuesday to finalise a 23-man squad, made it clear he would not call up Mamadou Sakho, even though media have reported the Liverpool defender's provisional 30-day ban for a failed drug test is unlikely to be extended by UEFA.
France were without striker Antoine Griezmann, who enjoyed a great season but was rested after his Atletico Madrid side lost to city rivals Real in Saturday's Champions League final.
Les Bleus will face Scotland in their final warm-up game on June 4 in Metz. They will play Romania in the opening game of the tournament on June 10 at the Stade de France and will also meet Albania and Switzerland in Group A.
(Writing by Patrick Vignal in Paris; Editing by Ken Ferris)
