Mine

CHOST="x86_64-pc-linux-gnu"
CFLAGS="-O2 -march=athlon64 -ffast-math -ftracer -fprefetch-loop-arrays -pipe -fforce-addr -ftree-vectorize"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O1 -Wl,--sort-common -Wl,--as-needed"
USE="-* 3dnow 3dnowext X a52 aac alsa amr berkdb bitmap-fonts bzip2 cairo cracklib crypt cups dbus \
	dri dvd dvdnav dvdread encode ffmpeg firefox flac gif gnome gtk hal jpeg mad mmx mmxext \
	mp3 mpeg ncurses no-old-linux nptl nptlonly nsplugin ogg opengl pam pcre perl pic png python \
	readline sdl sse sse2 ssl svg tcpd tiff truetype-fonts type1-fonts unicode usb vcd vorbis x264 \
	xinerama xml xv xvid zlib acpi tk"
ACCEPT_KEYWORDS="~amd64"
AUTOCLEAN="yes"
FEATURES="distlocks metadata-transfer sandbox sfperms strict"
INPUT_DEVICES="mouse keyboard synaptics"
VIDEO_CARDS="radeon fglrx"
PORTDIR_OVERLAY="/home/gentoo"