Is there a way to use my Xbox 360 on my iMac? If so, what cables do I need?
you can use thunderbolt as mini display port. that's not the point. maybe there is a application for that.depends, if you have a mac with a thunderbolt port, no. but if you have a mac with a minidisplayport, yes.
I have not done this personally, but this looks to be relevant:
http://macs.about.com/od/usingyourmac/qt/using-target-display-mode.htm