Yeah I did fluxbox with gdm, it doesn't install all of gnome, just the display manager.
I went
pacman -S fluxbox
pacman -S gdm
You can then edit /etc/inittab to have the runlevel be x11 after booting, or add xdm to startup by editing /etc/rc.conf.
I also went
pacman -S rox
and I added rox pinboard to my .fluxbox/startup. Because well I find fluxbox nearly unusable with a file roller! And rox is fast and lightweight.
I can hardly think of anything faster than arch running fluxbox + rox, besides of course only using console login.