Hosts Gabon's continued participation in the Africa Nations Cup was in serious doubt after they were held 1-1 by Burkina Faso on Wednesday, their second draw in Group A.
Pierre-Emerick Aubameyang again scored for his country but they had to come from behind to equalise and missed two good late chances to win the game.
Gabon and Burkina Faso have two points each from their opening two matches.
Prejuce Nakoulma put Burkina Faso ahead in the 22nd minute before Aubameyang equalised through a penalty.
|Pierre-Emerick Aubameyang was brought down in the box by goalkeeper Kouakou Herve Koffi|
Substitute Nakoulma, who had come on early when Burkina striker Jonathan Pitroipa appeared to suffer a serious knee injury, ran from the edge of his own penalty area on to a defensive clearance and got the better of full back Johan Obiang before gliding the ball into the net.
Burkina Faso's lead lasted 16 minutes before they were caught in similar circumstances as a long ball from Merlin Tandjigora was chased down by Aubameyang. He had his feet taken out from under him by goalkeeper Herve Koffi. The resultant penalty was neatly tucked away to the relief of the home crowd.
A stunning solo goal from Piqueti was not enough for Guinea Bissau as Cameroon came from behind to win 2-1 and take pole position in African Nations Cup Group A.
Piqueti powered through the Cameroon defence to give his side an early lead.
But Sebastien Siani equalised and Michael Ngadeu-Ngadjui struck what proved to be the winner as Cameroon clinched the first win of Group A.
The Indomitable Lions, who have four points, next play hosts Gabon in Sunday's final group game, while Guinea Bissau meet Burkina Faso.
Cameroon went close as Clinton Njie pulled the ball down at the back post, but Mamadou Cande blocked and Juary Soares blocked from Vincent Aboubakar.
Piqueti launched an attack from deep inside his own half, lifting the ball over Collins Fai before chasing on to it.
Substitute Robert Ndip Tambe dragged a shot wide across goal in stoppage time as Cameroon celebrated victory.