FIFA lists their U-20 WC star players on the individual team pages at their
official U-20 website. In this post, I've gone through and compiled all their 'star players' and have listed them in a single, easier to read list (with clubs).
CameroonFrancois Beyokol - (Canon Yaounde, Cameroon)
Charley Roussel Fomen - (Olympique Marseille, France)
Parfait Louis Essengue Eloumou - (Genoa, Italy)
Victor Cedric Nkoum - (Paris St. Germain, France)
EgyptMohamed Abougabal - (ENPPI, Egypt)
Mohamed Talaat - (Al-Ahly, Egypt)
GhanaRansford Osei - (Maccabi Haifa, Israel)
Dede Ayew - (Lorient, France)
David Addy - (Randers, Denmark)
Dominic Adiyiah - (Fredrikstad, Norway)
Abeiku Quansah - (Nice, France)
Jonathan Mensah - (Free State Stars, South Africa)
NigeriaRabiu Ibrahim - (Sporting Lisbon, Portugal)
Lukman Haruna - (AS Monaco, France)
South AfricaRamahlwe Mphahlele - (Moroka Swallows, South Africa)
Kermit Erasmus - (Excelsior, Netherlands)
Phumelele Bhengu - (Moroka Swallows, South Africa)
AustraliaJames Holland - (AZ Alkmaar, Netherlands)
Ben Kantarovski - (Newcastle United Jets, Australia)
Kofi Danning - (Sydney FC, Australia)
South KoreaCho Young-Cheol - (Albirex Niigata, Japan)
Koo Ja-Cheol - (Jeju United, South Korea)
UAEAhmed Khalil - (Al-Ahli, UAE)
Ahmed Ali - (Al-Wahda, UAE)
Theyab Awana - (Bani Yas, UAE)
UzbekistanSherzodbek Karimov - (Pakhtakor Tashkent, Uzbekistan)
Fozil Musaev - (Mash'al Mubarek, Uzbekistan)
Islom Tuhtahujaev - (Neftchi Farg'ona, Uzbekistan)
Davron Mirzayev - (Rubin Kazan, Russia)
Czech RepublicTomas Perkhart - (Slavia Prague, Czech, Loan from Tottenham)
Ondrej Mazuch - (Anderlecht, Belgium, Loan from Fiorentina)
Jan Sebek - (Chelsea, England)
EnglandMartin Kelly - (Liverpool, England)
Ben Mee - (Manchester City, England)
Michael Woods - (Chelsea, England)
Febian Brandy - (Manchester United, England)
GermanyRichard Sukuta-Pasu - (Bayer Leverkusen)
HungaryVlagyimir Koman - (Avellino, Italy)
Krisztian Nemeth - (Liverpool, England)
ItalyFabio Sciacca - (Catania, Italy)
Michelangelo Albertazzi - (AC Milan, Italy)
SpainFran Merida - (Arsenal, England)
Daniel Parejo - (Getafe, Spain, Loan from Real Madrid)
Sergio Asenjo - (Atletico Madrid, Spain)
Costa RicaJosue Martinez - (Saprissa, Costa Rica)
Marcos Urena - (Alajuelense, Costa Rica)
David Guzman - Saprissa, Costa Rica)
HondurasRoger Rojas - (Olimpia, Honduras, Loan from Wigan Athletic)
Mario Roberto Martinez - (Valerenga, Norway)
Wilmer Crisanto - (Victoria, Honduras)
Trinidad and TobagoSean de Silva - (College of Charleston, USA)
Jamal Gay - (Rot-Weiß Oberhausen, Germany)
Jake Thomson - (Southampton, England)
Marcus Joseph - (Joe Public, T&T)
USABrian Perk - (UCLA, USA)
Bryan Arguez - (Hertha Berlin, Germany)
Anthony Wallace - (FC Dallas, USA)
Brek Shea - (FC Dallas, USA)
TahitiTeheipuarii Hauata - (Tefana, Tahiti)
Lorenzo Tehau - (Terana, Tahiti)
Alvin Tehau - (Terana, Tahiti)
BrazilDouglas Costa - (Gremio)
Allan Kardec - (Vasco de Gama, Brazil, Loan from Internacional)
ParaguayHernan Perez - (Villarreal, Spain)
Robin Ariel Ramirez - (Libertad, Paraguay)
Federico Santander - (Guarani, Paraguay)
UruguayAbel Hernandez - (Palermo, Italy)
Adrian Gunino - (Boca Juniors, Argentina)
Leandro Cabrera - (Atletico Madrid, Spain)
Jonathan Urretavizcaya - (Benfica, Portugal)
VenezuelaRafael Romo - (Udinese, Italy)
Angelo Peña - (Braga, Portugal)
Jose Salomon Rondon - (Las Palmas, Spain)
Rafael Acosta - (Cagliari, Italy)