These are the files on my system belonging to fglrx. Maybe it's useful for you.
(I've removed a few files from the list, like docs and debug symbols. Those won't hurt anyone)
fglrx's kernel and xorg modules need to go.
Everything in /lib and /lib32 should go, too. Gentoo moves some stuff to /usr/lib/opengl/ati/lib/, those might be directly in /usr/lib/ for you. Also, /usr/lib/libGL.so is provided by both drivers, make sure not to remove the wrong one. If you delete it, you need to reinstall mesa.
Code:
/etc/ati/control
/etc/ati/atiogl.xml
/etc/ati/logo.xbm.example
/etc/ati/amdpcsdb.default
/etc/ati/logo_mask.xbm.example
/etc/ati/authatieventsd.sh
/etc/ati/signature
/etc/acpi/ati-powermode.sh
/etc/acpi/events/a-ac-aticonfig
/etc/acpi/events/a-lid-aticonfig
/etc/env.d/04ati-dri-path-amd64
/etc/env.d/04ati-dri-path-x86
/etc/env.d/03ati-colon-sep
/etc/conf.d/atieventsd
/etc/init.d/atieventsd
/lib/modules/2.6.29-gentoo-r5/video/fglrx.ko
/opt/bin/fglrxinfo
/opt/bin/aticonfig
/opt/bin/atiode
/opt/bin/amdcccle
/opt/bin/atiodcli
/opt/sbin/atieventsd
/usr/bin/fglrx_xgamma
/usr/bin/fgl_glxgears
/usr/sbin/atigetsysteminfo.sh
/usr/lib32/dri/fglrx_dri.so
/usr/lib32/opengl/ati/lib/libGL.so.1
/usr/lib32/opengl/ati/lib/libGL.so.1.2
/usr/lib32/opengl/ati/lib/libGL.la
/usr/lib32/opengl/ati/lib/libGL.so
/usr/lib32/opengl/ati/extensions/libglx.so
/usr/lib32/libatiuki.so.1.0
/usr/lib32/libaticalcl.so
/usr/lib32/libaticaldd.so
/usr/lib32/libaticalrt.so
/usr/lib64/dri/fglrx_dri.so
/usr/lib64/xorg/modules/linux/libfglrxdrm.so
/usr/lib64/xorg/modules/drivers/fglrx_drv.so
/usr/lib64/xorg/modules/glesx.so
/usr/lib64/xorg/modules/amdxmm.so
/usr/lib64/libfglrx_gamma.so
/usr/lib64/libAMDXvBA.so.1.0
/usr/lib64/libatiadlxx.so
/usr/lib64/libAMDXvBA.cap
/usr/lib64/libXvBAW.so.1.0
/usr/lib64/libfglrx_gamma.so.1
/usr/lib64/opengl/ati/lib/libGL.so.1
/usr/lib64/opengl/ati/lib/libGL.so.1.2
/usr/lib64/opengl/ati/lib/libGL.la
/usr/lib64/opengl/ati/lib/libGL.so
/usr/lib64/opengl/ati/extensions/libglx.so
/usr/lib64/libatiuki.so.1.0
/usr/lib64/libfglrx_dm.a
/usr/lib64/libfglrx_gamma.so.1.0
/usr/lib64/libfglrx_dm.so.1.0
/usr/lib64/libaticalcl.so
/usr/lib64/libaticaldd.so
/usr/lib64/libaticalrt.so
/usr/include/GL/glxATI.h
/usr/include/GL/glATI.h
/usr/include/ATI/GL/glx.h
/usr/include/ATI/GL/glxext.h
/usr/include/X11/extensions/fglrx_gamma.h