Cassidy or Marcus

[Wrath]

NPC's are good in early game, whoever they be, they're always a helpful hand. But that's all: in late game they're useful only to take the shots in your place, which means they must have an armor to take all the dmg and survive. So Marcus is out of question: he's to clumsy, and dumb (he always rush to enemies with his useless fists... it's nice when your fighting mole rats and other pityfull animals, but when an Enclave Guard faces you, Marcus will get killed veery easily, taking criticals all the time). So Cassidy is the best choice, althought I think you can do good without him. That is so if you're the kind of player who's more worried about upping your character than finishing the game with a cool ending. And that's why I gather as much teamattes as I can, just for fun, but when it comes to usefullness, get Cassidy and other resistant NPC's to share the damage you'd take.