As interactions between individuals are introduced into the freedom of choice literature by the mean of game forms, new issues appear. In particular, in this paper it is argued that individuals face uncertainty with respect to outcomes as they lose the control they implicitely exert over options in the opportunity set framework. A criterion is proposed as to compare alternative game forms in terms of the control they offer to individuals. The CardMin criterion suggests that any game form should be judged on the basis of the strategy offering the lowest number of pairwise different outcomes. An axiomatic characterization is provided in the case of two individuals.I acknowledge financial support from the Spanish Ministry of Education and Science through grants BEC2002-02130, SEJ2005-01481, 2005SGR00447 and FEDER, through contract PTA-2003-02-00005.