Here are a full list of files that you may want to edit, depending on your needs:

File Do I need to change it? Description
/etc/fstab YES - required Mount points for all filesystems to be used at boot time. This file must reflect your disk partition setup. We'll guide you through modifying this file below.
/etc/localtime Maybe - recommended Your timezone, which will default to UTC if not set. This should be a symbolic link to something located under /usr/share/zoneinfo (e.g. /usr/share/zoneinfo/America/Montreal)
/etc/make.conf (symlink) - also known as:
Maybe - recommended Parameters used by gcc (compiler), portage, and make. It's a good idea to set MAKEOPTS. This is covered later in this document.
/etc/conf.d/hostname Maybe - recommended Used to set system hostname. Set the hostname variable to the fully-qualified (with dots, ie. name if you have one. Otherwise, set to the local system hostname (without dots, ie. foo). Defaults to localhost if not set.
/etc/hosts No You no longer need to manually set the hostname in this file. This file is automatically generated by /etc/init.d/hostname.
/etc/conf.d/keymaps Optional Keyboard mapping configuration file (for console pseudo-terminals). Set if you have a non-US keyboard. See Funtoo Linux Localization.
/etc/conf.d/hwclock Optional How the time of the battery-backed hardware clock of the system is interpreted (UTC or local time). Linux uses the battery-backed hardware clock to initialize the system clock when the system is booted.
/etc/conf.d/modules Optional Kernel modules to load automatically at system startup. Typically not required. See Additional Kernel Resources for more info.
/etc/conf.d/consolefont Optional Allows you to specify the default console font. To apply this font, enable the consolefont service by running rc-update add consolefont.
profiles Optional Some useful portage settings that may help speed up intial configuration.