System Default Client vs. User Default Client

Can a user have a default client other than the system default client? If so, how? In R/3 profile, one is able to set the system default client. As soon as an user opens up its SAPGUI, the client number on the SAPGUI is set to the system default client. Occasionally, there are users who would like to have the client number set to something else, other than the system default client. How can we accomplish this?