The GDM (standard) login screen/theme for Fedora 10 isn't that good looking (a lot like the one from Fedora 9), if you need to impress a friend with 'looks' install KDM, and switch between GDM to KDM.

Here's how (as root):
$ yum install kdm
$ yum install system-switch-displaymanager
$ system-switch-displaymanager KDM