Team Leader:- Delta-38 from Republic Commando, experienced Mandalorian trained squad leader that can handle almost any mission from sabotage to a frontal assault and pull his own weight in a fight.
Weapons Expert:- John-117 from the Halo series, the Master Chief can pick up just about any weapon and tear up the enemy. Even weird alien weapons with technology he doesn't understand and that he has never even seen before let alone used are no problem for him, it helps he is a beast in a fight as well.
Muscle:- Jack from Mass Effect, a slightly weird choice but "muscle" describes her violent way of dealing with problems and despite her slight build she is physically strong with her insane Biotics on top of that. If stuff needs breaking or people need intimidating Jack is the one to do get it done.
Lone Wolf:- Adam Jensen from Dues Ex: Human revolution, he almost went in the stealth expert slot but he is well rounded and can deal with most situations and works well alone.
Stealth Expert: Others have picked him and so am I, Corvo Attano from Dishonoured. those magic abilities really make potent, being able to possess people and animals, teleport, see through walls and so on make him perfect for recon, surveillance and general infiltration.
Jack of all trades: Gordon Freeman, he can fight well and smart enough to solve most problems a team might face.
My teams secret sauce? All of them can cover other roles, most of them can fill in just as well in any of the roles as well as the one I put them in. Casualties and things happen, Jensen would make a good squad leader, stealth expert and Jack of all trades and the Chief would make a great Team leader, lone wolf and muscle for example.