My laptop is japanese so my keyboard is weird.
Under X use xmodmap to in order to have an altgr key.
What can I for the command line interface?
Use showkey to see the key's keycode.
Now, look at your keymap (you defined it in /etc/rc.conf). It is somewhere in /usr/share/kbd/keymaps/i386. In the keymap, look at the keysym associated with that keycode, if there is one. Verify also if the keymap includes the following line:
Either the keysym is not associated at all with a keycode (nor in the keymap directly, nor through the include directive), or it is associated to another keycode.
In both cases, the solution is to integrate the keymap with a personal keymap. You can put it where you like, mine is in /usr/local/share/kbd/keymaps/personal.map.
You need the following line in this file:
keycode <thekeycode> = AltGr
Now, as root, give the following command (it does not replace your keymap, but merely integrate it):
See if it works. If it works, you can automatize the integration at each boot putting the following in /etc/rc.local:
loadkeys -q /usr/local/share/kbd/keymaps/personal.map &> /dev/null &
Mortuus in anima, curam gero cutis
it works and it rox!